diff --git a/executor.go b/executor.go
index cd0b6653..d680d01f 100644
--- a/executor.go
+++ b/executor.go
@@ -255,7 +255,7 @@ func executeFieldsSerially(p executeFieldsParams) *Result {
 		p.Fields = map[string][]*ast.Field{}
 	}
 
-	finalResults := map[string]interface{}{}
+	finalResults := make(map[string]interface{}, len(p.Fields))
 	for responseName, fieldASTs := range p.Fields {
 		resolved, state := resolveField(p.ExecutionContext, p.ParentType, p.Source, fieldASTs)
 		if state.hasNoFieldDefs {
@@ -279,7 +279,7 @@ func executeFields(p executeFieldsParams) *Result {
 		p.Fields = map[string][]*ast.Field{}
 	}
 
-	finalResults := map[string]interface{}{}
+	finalResults := make(map[string]interface{}, len(p.Fields))
 	for responseName, fieldASTs := range p.Fields {
 		resolved, state := resolveField(p.ExecutionContext, p.ParentType, p.Source, fieldASTs)
 		if state.hasNoFieldDefs {
@@ -791,7 +791,7 @@ func completeListValue(eCtx *executionContext, returnType *List, fieldASTs []*as
 	}
 
 	itemType := returnType.OfType
-	completedResults := []interface{}{}
+	completedResults := make([]interface{}, 0, resultVal.Len())
 	for i := 0; i < resultVal.Len(); i++ {
 		val := resultVal.Index(i).Interface()
 		completedItem := completeValueCatchingError(eCtx, itemType, fieldASTs, info, val)