This essay is concerned with the planning and densification of suburbs, which present a huge challenge insofar as they form a large area of urbanized land that remains underexploited due to low residential density. Drawing on current research in the Paris city-region, the essay focuses specifically on the difficulty in implementing densification policies in low-rise suburban areas. It examines the varying degrees of densification fostered by these policies, and builds upon recent urban studies literature on suburban change to trace how suburban areas are being transformed through regulations, instruments and market dynamics associated with densification processes. What kinds of densification policy are being implemented and what are the socio-economic, political and cultural determinants of each type of regulatory approach? This essay will attempt to answer this question via an analysis of the densification policies being put in place in the municipalities of the Paris city-region. It will offer in turn a typology of these different policies. It shows that densification is an instrument that can be used to address local political concerns which vary greatly depending on the economic, social and geographical position of municipalities within larger urban areas.