diff --git a/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.cpp b/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.cpp
index 64ef27a63f..3137f12fcf 100644
--- a/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.cpp
+++ b/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.cpp
@@ -59,6 +59,8 @@ RimDerivedEnsembleCaseCollection::RimDerivedEnsembleCaseCollection()
     CAF_PDM_InitField( &m_caseCount, "CaseCount", QString( "" ), "Matching Cases", "", "", "" );
     m_caseCount.uiCapability()->setUiReadOnly( true );
 
+    CAF_PDM_InitField( &m_matchOnParameters, "MatchOnParameters", false, "Match On Parameters", "", "", "" );
+
     // Do not show child cases
     uiCapability()->setUiTreeChildrenHidden( true );
 
@@ -136,11 +138,19 @@ void RimDerivedEnsembleCaseCollection::updateDerivedEnsembleCases()
         auto crp = sumCase1->caseRealizationParameters();
         if ( !crp ) continue;
 
-        const auto& sumCase2 = findCaseByParametersHash( cases2, crp->parametersHash() );
-        if ( !sumCase2 ) continue;
+        RimSummaryCase* summaryCase2 = nullptr;
+        if ( m_matchOnParameters )
+        {
+            summaryCase2 = findCaseByParametersHash( cases2, crp->parametersHash() );
+        }
+        else
+        {
+            summaryCase2 = findCaseByRealizationNumber( cases2, crp->realizationNumber() );
+        }
+        if ( !summaryCase2 ) continue;
 
         auto derivedCase = firstCaseNotInUse();
-        derivedCase->setSummaryCases( sumCase1, sumCase2 );
+        derivedCase->setSummaryCases( sumCase1, summaryCase2 );
         derivedCase->setOperator( m_operator() );
         derivedCase->createSummaryReaderInterface();
         derivedCase->setCaseRealizationParameters( crp );
@@ -220,6 +230,7 @@ void RimDerivedEnsembleCaseCollection::defineUiOrdering( QString uiConfigName, c
     uiOrdering.add( &m_operator );
     uiOrdering.add( &m_ensemble2 );
     uiOrdering.add( &m_swapEnsemblesButton );
+    uiOrdering.add( &m_matchOnParameters );
 
     uiOrdering.skipRemainingFields( true );
 
@@ -238,7 +249,7 @@ void RimDerivedEnsembleCaseCollection::fieldChangedByUi( const caf::PdmFieldHand
     bool doUpdateCases = false;
     bool doShowDialog  = false;
 
-    if ( changedField == &m_ensemble1 || changedField == &m_ensemble2 )
+    if ( changedField == &m_ensemble1 || changedField == &m_ensemble2 || m_matchOnParameters )
     {
         doUpdate      = true;
         doUpdateCases = true;
@@ -408,6 +419,20 @@ RimSummaryCase* RimDerivedEnsembleCaseCollection::findCaseByParametersHash( cons
     return nullptr;
 }
 
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+RimSummaryCase* RimDerivedEnsembleCaseCollection::findCaseByRealizationNumber( const std::vector<RimSummaryCase*>& cases,
+                                                                               int realizationNumber ) const
+{
+    for ( auto sumCase : cases )
+    {
+        auto ensembleParameters = sumCase->caseRealizationParameters();
+        if ( ensembleParameters && ensembleParameters->realizationNumber() == realizationNumber ) return sumCase;
+    }
+    return nullptr;
+}
+
 //--------------------------------------------------------------------------------------------------
 ///
 //--------------------------------------------------------------------------------------------------
diff --git a/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.h b/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.h
index dba659b60c..743ce8c65e 100644
--- a/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.h
+++ b/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.h
@@ -73,7 +73,10 @@ private:
     RimDerivedSummaryCase*              firstCaseNotInUse();
     std::vector<RimDerivedSummaryCase*> allDerivedCases( bool activeOnly ) const;
     void                                updateAutoName();
+
     RimSummaryCase* findCaseByParametersHash( const std::vector<RimSummaryCase*>& cases, size_t hash ) const;
+    RimSummaryCase* findCaseByRealizationNumber( const std::vector<RimSummaryCase*>& cases, int realizationNumber ) const;
+
     std::vector<RimDerivedEnsembleCaseCollection*> findReferringEnsembles() const;
 
 private:
@@ -85,4 +88,5 @@ private:
     caf::PdmField<caf::AppEnum<DerivedSummaryOperator>> m_operator;
     caf::PdmField<bool>                                 m_swapEnsemblesButton;
     caf::PdmField<QString>                              m_caseCount;
+    caf::PdmField<bool>                                 m_matchOnParameters;
 };
diff --git a/ApplicationCode/ProjectDataModel/Summary/RimSummaryCaseMainCollection.cpp b/ApplicationCode/ProjectDataModel/Summary/RimSummaryCaseMainCollection.cpp
index 966f487c51..974674e551 100644
--- a/ApplicationCode/ProjectDataModel/Summary/RimSummaryCaseMainCollection.cpp
+++ b/ApplicationCode/ProjectDataModel/Summary/RimSummaryCaseMainCollection.cpp
@@ -66,7 +66,7 @@ void addCaseRealizationParametersIfFound( RimSummaryCase& sumCase, const QString
 
     int realizationNumber = RifCaseRealizationParametersFileLocator::realizationNumber( modelFolderOrFile );
     parameters->setRealizationNumber( realizationNumber );
-    parameters->addParameter( "REALIZATION_NUM", realizationNumber );
+    parameters->addParameter( "RI:REALIZATION_NUM", realizationNumber );
 
     sumCase.setCaseRealizationParameters( parameters );
 }