The present study investigates the relation between urban form and the socio-economic patterns of the resident population in three southern European cities (Athens, Lisbon and Rome) featured by different processes of urban diffusion. The paper goes beyond the literature on sprawl focused on (residential, income and ethnic) segregation and the different features of the inhabitants of the suburbs and those of the inner cities residents. By integrating multivariate statistics and spatial analysis, a methodology is proposed, based on morphological and socio-economic indicators available at a fine geographical scale. Results show how urban diffusion processes vary widely according to the context, as does the socio-economic profile of the actors, stressing the need to think about different 'southern European alternatives' of sprawl.