Producer services are believed to be leaving central business districts. In the Paris region, deconcentration is rather one of polarisation than dispersal. The twenty main producer services centres shape a growing poly-nuclear pattern. Its reinforcement, especially with the development of outer suburbs poles, induces the fragmentation of a once unified workforce market. Yet the geography of intra-metropolitan economic interactions differs. The study of business calls made by the Ile-de-France firms unravels a polycentric system where concentration in the denser part of the agglomeration is still crucial. The central metropolitan triangle of Paris – La Défense – Boulogne is an informational district that exchanges large amount of internal information flows and integrates infra-regional sub-networks that would hardly be connected otherwise. The Parisian model is one of a hierarchical polycentricity which stresses the importance of proximity in the metropolitan economic system.