diff --git a/pkg/promlib/models/scope.go b/pkg/promlib/models/scope.go
index 3fd7a62b8eb..41fbbb43444 100644
--- a/pkg/promlib/models/scope.go
+++ b/pkg/promlib/models/scope.go
@@ -73,11 +73,31 @@ func ApplyFiltersAndGroupBy(rawExpr string, scopeFilters, adHocFilters []ScopeFi
 func FiltersToMatchers(scopeFilters, adhocFilters []ScopeFilter) ([]*labels.Matcher, error) {
 	filterMap := make(map[string]*labels.Matcher)
 
-	for _, filter := range append(scopeFilters, adhocFilters...) {
+	// scope filters are applied first
+	for _, filter := range scopeFilters {
 		matcher, err := filterToMatcher(filter)
 		if err != nil {
 			return nil, err
 		}
+
+		// when scopes have the same key, both values should be matched
+		// in prometheus that means using an regex with both values
+		if _, ok := filterMap[filter.Key]; ok {
+			filterMap[filter.Key].Value = filterMap[filter.Key].Value + "|" + matcher.Value
+			filterMap[filter.Key].Type = labels.MatchRegexp
+		} else {
+			filterMap[filter.Key] = matcher
+		}
+	}
+
+	// ad hoc filters are applied after scope filters
+	for _, filter := range adhocFilters {
+		matcher, err := filterToMatcher(filter)
+		if err != nil {
+			return nil, err
+		}
+
+		// when ad hoc filters have the same key, the last one should be used
 		filterMap[filter.Key] = matcher
 	}
 
diff --git a/pkg/promlib/models/scope_test.go b/pkg/promlib/models/scope_test.go
index 4799b148835..fc7d972eb44 100644
--- a/pkg/promlib/models/scope_test.go
+++ b/pkg/promlib/models/scope_test.go
@@ -106,6 +106,29 @@ func TestApplyQueryFiltersAndGroupBy_Filters(t *testing.T) {
 			expected:  `{__name__="http_requests_total",namespace="istio"}`,
 			expectErr: false,
 		},
+		{
+			name:  "merge scopes filters into using OR if they share filter key",
+			query: `http_requests_total{}`,
+			scopeFilters: []ScopeFilter{
+				{Key: "namespace", Value: "default", Operator: FilterOperatorEquals},
+				{Key: "namespace", Value: "kube-system", Operator: FilterOperatorEquals},
+			},
+			expected:  `http_requests_total{namespace=~"default|kube-system"}`,
+			expectErr: false,
+		},
+		{
+			name:  "adhoc filters win over scope filters if they share filter key",
+			query: `http_requests_total{}`,
+			scopeFilters: []ScopeFilter{
+				{Key: "namespace", Value: "default", Operator: FilterOperatorEquals},
+				{Key: "namespace", Value: "kube-system", Operator: FilterOperatorEquals},
+			},
+			adhocFilters: []ScopeFilter{
+				{Key: "namespace", Value: "adhoc-wins", Operator: FilterOperatorEquals},
+			},
+			expected:  `http_requests_total{namespace="adhoc-wins"}`,
+			expectErr: false,
+		},
 	}
 
 	for _, tt := range tests {
@@ -116,7 +139,7 @@ func TestApplyQueryFiltersAndGroupBy_Filters(t *testing.T) {
 				require.Error(t, err)
 			} else {
 				require.NoError(t, err)
-				require.Equal(t, tt.expected, expr)
+				require.Equal(t, tt.expected, expr, tt.name)
 			}
 		})
 	}