diff --git a/icu4c/source/i18n/formattedval_impl.h b/icu4c/source/i18n/formattedval_impl.h
index 837e89b..4cfb0f0 100644
--- a/icu4c/source/i18n/formattedval_impl.h
+++ b/icu4c/source/i18n/formattedval_impl.h
@@ -117,6 +117,12 @@
 };
 
 
+// Internal struct that must be exported for MSVC
+struct U_I18N_API SpanInfo {
+    int32_t spanValue;
+    int32_t length;
+};
+
 // Export an explicit template instantiation of the MaybeStackArray that
 //    is used as a data member of CEBuffer.
 //
@@ -126,7 +132,7 @@
 // See digitlst.h, pluralaffix.h, datefmt.h, and others for similar examples.
 //
 #if U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN
-template class U_I18N_API MaybeStackArray<int32_t, 8>;
+template class U_I18N_API MaybeStackArray<SpanInfo, 8>;
 #endif
 
 /**
@@ -162,13 +168,19 @@
         return fString;
     }
 
-    void appendSpanIndex(int32_t index);
-    void prependSpanIndex(int32_t index);
+    /**
+     * Adds additional metadata used for span fields.
+     * 
+     * spanValue: the index of the list item, for example.
+     * length: the length of the span, used to split adjacent fields.
+     */
+    void appendSpanInfo(int32_t spanValue, int32_t length);
+    void prependSpanInfo(int32_t spanValue, int32_t length);
 
 private:
     FormattedStringBuilder fString;
     FormattedStringBuilder::Field fNumericField;
-    MaybeStackArray<int32_t, 8> spanIndices;
+    MaybeStackArray<SpanInfo, 8> spanIndices;
 
     bool nextPositionImpl(ConstrainedFieldPosition& cfpos, FormattedStringBuilder::Field numericField, UErrorCode& status) const;
     static bool isIntOrGroup(FormattedStringBuilder::Field field);
diff --git a/icu4c/source/i18n/formattedval_sbimpl.cpp b/icu4c/source/i18n/formattedval_sbimpl.cpp
index b2ae4c3..aad4438 100644
--- a/icu4c/source/i18n/formattedval_sbimpl.cpp
+++ b/icu4c/source/i18n/formattedval_sbimpl.cpp
@@ -46,19 +46,19 @@
 
 UBool FormattedValueStringBuilderImpl::nextPosition(ConstrainedFieldPosition& cfpos, UErrorCode& status) const {
     // NOTE: MSVC sometimes complains when implicitly converting between bool and UBool
-    return nextPositionImpl(cfpos, fNumericField, status) ? TRUE : FALSE;
+    return nextPositionImpl(cfpos, fNumericField, status) ? true : false;
 }
 
 UBool FormattedValueStringBuilderImpl::nextFieldPosition(FieldPosition& fp, UErrorCode& status) const {
     int32_t rawField = fp.getField();
 
     if (rawField == FieldPosition::DONT_CARE) {
-        return FALSE;
+        return false;
     }
 
     if (rawField < 0 || rawField >= UNUM_FIELD_COUNT) {
         status = U_ILLEGAL_ARGUMENT_ERROR;
-        return FALSE;
+        return false;
     }
 
     ConstrainedFieldPosition cfpos;
@@ -67,7 +67,7 @@
     if (nextPositionImpl(cfpos, kUndefinedField, status)) {
         fp.setBeginIndex(cfpos.getStart());
         fp.setEndIndex(cfpos.getLimit());
-        return TRUE;
+        return true;
     }
 
     // Special case: fraction should start after integer if fraction is not present
@@ -85,7 +85,7 @@
         fp.setEndIndex(i - fString.fZero);
     }
 
-    return FALSE;
+    return false;
 }
 
 void FormattedValueStringBuilderImpl::getAllFieldPositions(FieldPositionIteratorHandler& fpih,
@@ -103,23 +103,12 @@
 bool FormattedValueStringBuilderImpl::nextPositionImpl(ConstrainedFieldPosition& cfpos, Field numericField, UErrorCode& /*status*/) const {
     int32_t fieldStart = -1;
     Field currField = kUndefinedField;
-    UFieldCategory spanCategory = UFIELD_CATEGORY_UNDEFINED;
-    int32_t spanValue;
     for (int32_t i = fString.fZero + cfpos.getLimit(); i <= fString.fZero + fString.fLength; i++) {
         Field _field = (i < fString.fZero + fString.fLength) ? fString.getFieldPtr()[i] : kEndField;
         // Case 1: currently scanning a field.
         if (currField != kUndefinedField) {
             if (currField != _field) {
                 int32_t end = i - fString.fZero;
-                // Handle span fields; don't trim them
-                if (spanCategory != UFIELD_CATEGORY_UNDEFINED) {
-                    cfpos.setState(
-                        spanCategory,
-                        spanValue,
-                        fieldStart,
-                        end);
-                    return true;
-                }
                 // Grouping separators can be whitespace; don't throw them out!
                 if (isTrimmable(currField)) {
                     end = trimBack(i - fString.fZero);
@@ -182,13 +171,11 @@
             if (elementField == Field(UFIELD_CATEGORY_LIST, ULISTFMT_ELEMENT_FIELD)
                     && cfpos.matchesField(elementField.getCategory(), elementField.getField())
                     && (cfpos.getLimit() < i - fString.fZero || cfpos.getCategory() != elementField.getCategory())) {
-                // Re-wind to the beginning of the field and then emit it
-                int32_t j = i - 1;
-                for (; j >= fString.fZero && fString.getFieldPtr()[j] == fString.getFieldPtr()[i-1]; j--) {}
+                int64_t si = cfpos.getInt64IterationContext() - 1;
                 cfpos.setState(
                     elementField.getCategory(),
                     elementField.getField(),
-                    j - fString.fZero + 1,
+                    i - fString.fZero - spanIndices[si].length,
                     i - fString.fZero);
                 return true;
             }
@@ -203,22 +190,28 @@
         }
         // Case 3: check for field starting at this position
         // Case 3a: Need to add a SpanField
-        if (_field == Field(UFIELD_CATEGORY_LIST, ULISTFMT_ELEMENT_FIELD)
-                // don't return the same field twice in a row:
-                && (i == fString.fZero
-                    || fString.getFieldPtr()[i-1].getCategory() != UFIELD_CATEGORY_LIST
-                    || fString.getFieldPtr()[i-1].getField() != ULISTFMT_ELEMENT_FIELD)) {
+        if (_field == Field(UFIELD_CATEGORY_LIST, ULISTFMT_ELEMENT_FIELD)) {
             int64_t si = cfpos.getInt64IterationContext();
-            spanValue = spanIndices[si];
+            int32_t spanValue = spanIndices[si].spanValue;
+            int32_t length = spanIndices[si].length;
             cfpos.setInt64IterationContext(si + 1);
             if (cfpos.matchesField(UFIELD_CATEGORY_LIST_SPAN, spanValue)) {
-                spanCategory = UFIELD_CATEGORY_LIST_SPAN;
+                UFieldCategory spanCategory = UFIELD_CATEGORY_LIST_SPAN;
                 fieldStart = i - fString.fZero;
-                currField = _field;
+                int32_t end = fieldStart + length;
+                cfpos.setState(
+                    spanCategory,
+                    spanValue,
+                    fieldStart,
+                    end);
+                return true;
+            } else {
+                // Failed to match; jump ahead
+                i += length - 1;
                 continue;
             }
         }
-        // Case 3b: No SpanField or SpanField did not match
+        // Case 3b: No SpanField
         if (cfpos.matchesField(_field.getCategory(), _field.getField())) {
             fieldStart = i - fString.fZero;
             currField = _field;
@@ -229,21 +222,21 @@
     return false;
 }
 
-void FormattedValueStringBuilderImpl::appendSpanIndex(int32_t position) {
-    if (spanIndices.getCapacity() <= position) {
-        spanIndices.resize(position * 2);
+void FormattedValueStringBuilderImpl::appendSpanInfo(int32_t spanValue, int32_t length) {
+    if (spanIndices.getCapacity() <= spanValue) {
+        spanIndices.resize(spanValue * 2);
     }
-    spanIndices[position] = position;
+    spanIndices[spanValue] = {spanValue, length};
 }
 
-void FormattedValueStringBuilderImpl::prependSpanIndex(int32_t position) {
-    if (spanIndices.getCapacity() <= position) {
-        spanIndices.resize(position * 2);
+void FormattedValueStringBuilderImpl::prependSpanInfo(int32_t spanValue, int32_t length) {
+    if (spanIndices.getCapacity() <= spanValue) {
+        spanIndices.resize(spanValue * 2);
     }
-    for (int32_t i = 0; i < position; i++) {
+    for (int32_t i = spanValue - 1; i >= 0; i--) {
         spanIndices[i+1] = spanIndices[i];
     }
-    spanIndices[0] = position;
+    spanIndices[0] = {spanValue, length};
 }
 
 bool FormattedValueStringBuilderImpl::isIntOrGroup(Field field) {
diff --git a/icu4c/source/i18n/listformatter.cpp b/icu4c/source/i18n/listformatter.cpp
index 66d76b5..2ee646f 100644
--- a/icu4c/source/i18n/listformatter.cpp
+++ b/icu4c/source/i18n/listformatter.cpp
@@ -567,7 +567,7 @@
                 start,
                 {UFIELD_CATEGORY_LIST, ULISTFMT_ELEMENT_FIELD},
                 status);
-            data->appendSpanIndex(0);
+            data->appendSpanInfo(0, start.length());
         }
     }
 
@@ -603,7 +603,7 @@
                 next,
                 {UFIELD_CATEGORY_LIST, ULISTFMT_ELEMENT_FIELD},
                 status);
-            data->appendSpanIndex(position);
+            data->appendSpanInfo(position, next.length());
             data->getStringRef().append(
                 temp.tempSubString(offsets[1]),
                 {UFIELD_CATEGORY_LIST, ULISTFMT_LITERAL_FIELD},
@@ -622,7 +622,7 @@
                 next,
                 {UFIELD_CATEGORY_LIST, ULISTFMT_ELEMENT_FIELD},
                 status);
-            data->prependSpanIndex(position);
+            data->prependSpanInfo(position, next.length());
             data->getStringRef().insert(
                 0,
                 temp.tempSubStringBetween(0, offsets[1]),
diff --git a/icu4c/source/test/intltest/listformattertest.cpp b/icu4c/source/test/intltest/listformattertest.cpp
index c57c8f5..c96e2a0 100644
--- a/icu4c/source/test/intltest/listformattertest.cpp
+++ b/icu4c/source/test/intltest/listformattertest.cpp
@@ -48,6 +48,7 @@
     TESTCASE_AUTO(TestBadStylesFail);
     TESTCASE_AUTO(TestCreateStyled);
     TESTCASE_AUTO(TestContextual);
+    TESTCASE_AUTO(TestNextPosition);
     TESTCASE_AUTO_END;
 }
 
@@ -494,10 +495,10 @@
 
 void ListFormatterTest::TestFormattedValue() {
     IcuTestErrorCode status(*this, "TestFormattedValue");
-    LocalPointer<ListFormatter> fmt(ListFormatter::createInstance("en", status));
-    if (status.errIfFailureAndReset()) { return; }
 
     {
+        LocalPointer<ListFormatter> fmt(ListFormatter::createInstance("en", status));
+        if (status.errIfFailureAndReset()) { return; }
         const char16_t* message = u"Field position test 1";
         const char16_t* expectedString = u"hello, wonderful, and world";
         const UnicodeString inputs[] = {
@@ -523,6 +524,33 @@
             expectedFieldPositions,
             UPRV_LENGTHOF(expectedFieldPositions));
     }
+
+    {
+        LocalPointer<ListFormatter> fmt(ListFormatter::createInstance("zh", ULISTFMT_TYPE_UNITS, ULISTFMT_WIDTH_SHORT, status));
+        if (status.errIfFailureAndReset()) { return; }
+        const char16_t* message = u"Field position test 2 (ICU-21340)";
+        const char16_t* expectedString = u"aabbbbbbbccc";
+        const UnicodeString inputs[] = {
+            u"aa",
+            u"bbbbbbb",
+            u"ccc"
+        };
+        FormattedList result = fmt->formatStringsToValue(inputs, UPRV_LENGTHOF(inputs), status);
+        static const UFieldPositionWithCategory expectedFieldPositions[] = {
+            // field, begin index, end index
+            {UFIELD_CATEGORY_LIST_SPAN, 0, 0, 2},
+            {UFIELD_CATEGORY_LIST, ULISTFMT_ELEMENT_FIELD, 0, 2},
+            {UFIELD_CATEGORY_LIST_SPAN, 1, 2, 9},
+            {UFIELD_CATEGORY_LIST, ULISTFMT_ELEMENT_FIELD, 2, 9},
+            {UFIELD_CATEGORY_LIST_SPAN, 2, 9, 12},
+            {UFIELD_CATEGORY_LIST, ULISTFMT_ELEMENT_FIELD, 9, 12}};
+        checkMixedFormattedValue(
+            message,
+            result,
+            expectedString,
+            expectedFieldPositions,
+            UPRV_LENGTHOF(expectedFieldPositions));
+    }
 }
 
 void ListFormatterTest::DoTheRealListStyleTesting(Locale locale,
@@ -700,4 +728,50 @@
     }
 }
 
+void ListFormatterTest::TestNextPosition() {
+    IcuTestErrorCode status(*this, "TestNextPosition");
+    std::vector<std::string> locales = { "en", "es", "zh", "ja" };
+    UListFormatterWidth widths [] = {
+        ULISTFMT_WIDTH_WIDE, ULISTFMT_WIDTH_SHORT, ULISTFMT_WIDTH_NARROW
+    };
+    const char* widthStr [] = {"wide", "short", "narrow"};
+    UListFormatterType types [] = {
+        ULISTFMT_TYPE_AND, ULISTFMT_TYPE_OR, ULISTFMT_TYPE_UNITS
+    };
+    const char* typeStr [] = {"and", "or", "units"};
+    const UnicodeString inputs[] = { u"A1", u"B2", u"C3", u"D4" };
+    for (auto width : widths) {
+        for (auto type : types) {
+            for (auto locale : locales) {
+                LocalPointer<ListFormatter> fmt(
+                        ListFormatter::createInstance(locale.c_str(), type, width, status),
+                    status);
+                if (status.errIfFailureAndReset()) {
+                    continue;
+                }
+                for (int32_t n = 1; n <= UPRV_LENGTHOF(inputs); n++) {
+                    FormattedList result = fmt->formatStringsToValue(
+                        inputs, n, status);
+                    int32_t elements = 0;
+                    icu::ConstrainedFieldPosition cfpos;
+                    cfpos.constrainCategory(UFIELD_CATEGORY_LIST);
+                    while (result.nextPosition(cfpos, status) && U_SUCCESS(status)) {
+                        if (cfpos.getField() == ULISTFMT_ELEMENT_FIELD) {
+                            elements++;
+                        }
+                    }
+                    std::string msg = locale;
+                    // Test that if there are n elements (n=1..4) in the input, then the
+                    // nextPosition() should iterate through exactly n times
+                    // with field == ULISTFMT_ELEMENT_FIELD.
+                    assertEquals((msg
+                                  .append(" w=").append(widthStr[width])
+                                  .append(" t=").append(typeStr[type])).c_str(),
+                                 n, elements);
+                }
+            }
+        }
+    }
+}
+
 #endif /* #if !UCONFIG_NO_FORMATTING */
diff --git a/icu4c/source/test/intltest/listformattertest.h b/icu4c/source/test/intltest/listformattertest.h
index 9c7a5dd..b3d4005 100644
--- a/icu4c/source/test/intltest/listformattertest.h
+++ b/icu4c/source/test/intltest/listformattertest.h
@@ -55,6 +55,7 @@
     void TestBadStylesFail();
     void TestCreateStyled();
     void TestContextual();
+    void TestNextPosition();
 
   private:
     void CheckFormatting(