diff --git a/moto/swf/models/__init__.py b/moto/swf/models/__init__.py
index 2c040f8db..9fff96ebb 100644
--- a/moto/swf/models/__init__.py
+++ b/moto/swf/models/__init__.py
@@ -180,16 +180,16 @@ class SWFBackend(BaseBackend):
         # aren't distributed.
         #
         # TODO: handle long polling (case 2) for decision tasks
-        decision_candidates = []
-        for _, wfe in domain.workflow_executions.iteritems():
-            if wfe.task_list == task_list:
-                decision_candidates += wfe.scheduled_decision_tasks
-        if any(decision_candidates):
+        candidates = []
+        for _task_list, tasks in domain.decision_task_lists.iteritems():
+            if _task_list == task_list:
+                candidates += filter(lambda t: t.state == "SCHEDULED", tasks)
+        if any(candidates):
             # TODO: handle task priorities (but not supported by boto for now)
-            decision = min(decision_candidates, key=lambda d: d.scheduled_at)
-            wfe = decision.workflow_execution
-            wfe.start_decision_task(decision.task_token, identity=identity)
-            return decision
+            task = min(candidates, key=lambda d: d.scheduled_at)
+            wfe = task.workflow_execution
+            wfe.start_decision_task(task.task_token, identity=identity)
+            return task
         else:
             return None
 
diff --git a/moto/swf/models/workflow_execution.py b/moto/swf/models/workflow_execution.py
index a9a277254..0b1984af2 100644
--- a/moto/swf/models/workflow_execution.py
+++ b/moto/swf/models/workflow_execution.py
@@ -182,13 +182,6 @@ class WorkflowExecution(object):
             self.domain.decision_tasks
         )
 
-    @property
-    def scheduled_decision_tasks(self):
-        return filter(
-            lambda t: t.state == "SCHEDULED",
-            self.decision_tasks
-        )
-
     @property
     def activity_tasks(self):
         return filter(