How to turn a hierarchy into a flat structure in query

Ok, we're having a query with a 0ACCOUNT hierarchy. Problem is, we don't want it to be displayed as a hierarchy but as a flat structure. As soon as I turn off the hierarchy within the Query (via mouse-click on column --> Properties --> Hierarchies --> turn off display by unchecking button) the query displays accounts that aren't part of the hierarchy.

Ideas anyone? And thanks in advance.