The recent urban dynamics of industrialised countries show the rise of a new spatial order, which simplifies 'vertical' relationships between the cities and complicates, instead, the 'horizontal' inter-urban patterns. Some northern Italian regions, such as Lombardy, Veneto and Emilia-Romagna, have been characterised historically by polycentric settlement, which constitutes today the spatial texture of functional, economic and social relationships among the urban places, their hinterlands and their regions, according to a new order of spatial organisation. This is a network-based order, whose theoretical framework is not still well founded. The aim of this paper is to contribute to the establishment of a new theoretical paradigm, by integrating several taxonomies recently proposed by Italian researchers in urban and regional sciences. Obviously, the results of these reflections are still weak and open to further contributions, particularly with regard to other regions in north-western Europe.