Over the past decades, demographic changes, advances in transportation and communication technology, and the growth of the services sector have had a significant impact on the spatial structure of regions. Monocentric cities are disappearing and developing into polycentric metropolitan areas, while at the same time, social economic processes are taking place at an ever larger geographical scale, beyond that of the city, in which historically separate metropolitan areas are becoming increasingly functionally connected to form polycentric urban regions. Such urban networks are characterised by the lack of an urban hierarchy, a significant degree of spatial integration between different cities and, complementary relationships between centres, in that cities and towns have different economic specialisations. The growing literature on changing urban systems coincides with the increasing popularity of the urban network concept in contemporary spatial planning and policy, in which urban networks are often seen as a panacea for regional economic development problems. Polycentricity and spatial integration have become catchphrases, where polycentric development policies have been introduced to support territorial cohesion as well as higher levels of territorial competitiveness. Despite the enthusiasm for the ideas of a polycentric and networked spatial organisation, the assessment of the network concept leaves much to be desired. To what extent are regions becoming more polycentric and spatially integrated? Are relationships between cities in polycentric, spatially integrated regions complementary rather than competitive? And are polycentric, spatially integrated regions more economically efficient than their monocentric, non-integrated counterparts? In this study, these questions will be addressed.