In this thesis I analyze how national spatial plans that have been adopted in European countries during the last decade have interpreted the polycentric development concept. A survey revealed that fifteen European countries have developed a national spatial plan and the formal influence of the European Spatial Development Perspective (ESDP) is clearly demonstrated in these plans. The development visions presented in the spatial planning documents are, at a formal level, relatively homogenous regardless of national differences regarding the size of the population and the geographical area. In the thesis I also pose the question whether the national spatial plans will contribute towards a polycentric development on a European level. The findings presented in the thesis suggest that even though the national spatial plans have been inspired by the ESDP and its aim of developing a polycentric development the interpretation of polycentrism on the national level seem to be contradictory to the policy aim at the European level. Also, the Swedish planning experience of the 1960/70s highlights the difficult task of prioritising the development in some cities at the expense of others. Thus, it is concluded that even if the spatial plans are better coordinated so that they contribute towards a common spatial vision it is still highly doubtful that they will be able to deliver on their objective to create a more balanced urban system.