diff --git a/ApplicationCode/ProjectDataModel/Summary/RimEnsembleCurveSet.cpp b/ApplicationCode/ProjectDataModel/Summary/RimEnsembleCurveSet.cpp
index 4cb05f2da7..6dbb34dd3c 100644
--- a/ApplicationCode/ProjectDataModel/Summary/RimEnsembleCurveSet.cpp
+++ b/ApplicationCode/ProjectDataModel/Summary/RimEnsembleCurveSet.cpp
@@ -1028,7 +1028,6 @@ void RimEnsembleCurveSet::updateStatisticsCurves(const std::vector<RimSummaryCas
         curve->setSummaryCaseY(m_ensembleStatCase.get());
         curve->setSummaryAddressY(address);
         curve->setLeftOrRightAxisY(m_plotAxis());
-        curve->setZOrder(1000);
 
         curve->updateCurveVisibility(false);
         curve->loadDataAndUpdate(false);
diff --git a/ApplicationCode/ProjectDataModel/Summary/RimSummaryCurve.cpp b/ApplicationCode/ProjectDataModel/Summary/RimSummaryCurve.cpp
index 3f06e82ace..fbc1cc8630 100644
--- a/ApplicationCode/ProjectDataModel/Summary/RimSummaryCurve.cpp
+++ b/ApplicationCode/ProjectDataModel/Summary/RimSummaryCurve.cpp
@@ -164,6 +164,7 @@ void RimSummaryCurve::setSummaryCaseY(RimSummaryCase* sumCase)
     }
 
     m_yValuesSummaryCase = sumCase;
+    setZIndexFromCurveInfo();
 }
 
 //--------------------------------------------------------------------------------------------------
@@ -211,6 +212,7 @@ void RimSummaryCurve::setSummaryAddressY(const RifEclipseSummaryAddress& address
     }
 
     m_yValuesCurveVariable->setAddress(address);
+    setZIndexFromCurveInfo();
 
     m_yValuesSummaryFilter->updateFromAddress(address);
 
@@ -660,6 +662,44 @@ void RimSummaryCurve::appendOptionItemsForSummaryAddresses(QList<caf::PdmOptionI
     }
 }
 
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+void RimSummaryCurve::setZIndexFromCurveInfo()
+{
+    // Z index. Higher Z is painted in front
+    enum ZIndex
+    {
+        Z_ENSEMBLE_CURVE = 100,
+        Z_ENSEMBLE_STAT_CURVE = 200,
+        Z_SINGLE_CURVE_NON_OBSERVED = 300,
+        Z_SINGLE_CURVE_OBSERVED = 400
+    };
+
+    auto sumAddr = summaryAddressY();
+    auto sumCase = summaryCaseY();
+
+    if (sumCase && sumAddr.isValid())
+    {
+        if (sumCase->isObservedData())
+        {
+            setZOrder(Z_SINGLE_CURVE_OBSERVED);
+        }
+        else if (sumAddr.category() == RifEclipseSummaryAddress::SUMMARY_ENSEMBLE_STATISTICS)
+        {
+            setZOrder(Z_ENSEMBLE_STAT_CURVE);
+        }
+        else if (sumCase->ensemble())
+        {
+            setZOrder(Z_ENSEMBLE_CURVE);
+        }
+        else
+        {
+            setZOrder(Z_SINGLE_CURVE_NON_OBSERVED);
+        }
+    }
+}
+ 
 //--------------------------------------------------------------------------------------------------
 /// 
 //--------------------------------------------------------------------------------------------------
diff --git a/ApplicationCode/ProjectDataModel/Summary/RimSummaryCurve.h b/ApplicationCode/ProjectDataModel/Summary/RimSummaryCurve.h
index 7ae8d0ea0a..1e0258e118 100644
--- a/ApplicationCode/ProjectDataModel/Summary/RimSummaryCurve.h
+++ b/ApplicationCode/ProjectDataModel/Summary/RimSummaryCurve.h
@@ -106,6 +106,7 @@ private:
     static void                             appendOptionItemsForSummaryAddresses(QList<caf::PdmOptionItemInfo>* options,
                                                                                  RimSummaryCase* summaryCase,
                                                                                  RimSummaryFilter* summaryFilter);
+    void                            setZIndexFromCurveInfo();
 
 private:
     // Y values