While recent studies have illustrated how European cities are shifting towards exurban development, the influence of urban form on sprawl models has been poorly investigated at both the regional and local scales. The present study introduces an original sprawl index and analyses its spatio-temporal dynamics between 1960 and 2010 in two Mediterranean regions (Athens and Rome) characterized by contrasting urban morphology. Different models of urban dispersion have been identified during the investigated period by correlating variables such as population density, land-use and territorial characteristics to the sprawl index. This index significantly diverged in the two regions, suggesting that recent urbanization patterns are influenced by the city’s form. The results contribute to the debate on sustainable urban form for expanding cities in Europe.