National spatial policies are usually indicative and strategic. As a result, this kind of policy does not have a direct bearing on the spatial organisation of society. Instead the performance of these policies depends on whether or not they are used in subsequent decisionmaking and planning procedures, where and when this seems relevant. Consequently, straightforward evaluation procedures, based on a combined methodology of before - after design and the measurement of conformity, do not help us to understand the real influence of these policies. Insight into the 'black box' of subsequent deciosionmaking is necessary for this purpose. In this paper we discuss some recent research findings on this topic.