Urban concentration which implies multifamily housing is one of the solutions planned to carry out a sustainable development. In this context, it was interesting to study the way in which human density is lived in large residential buildings. Furthermore, few studies have been done in France about psychological reactions to density. 162 inhabitants of three large residential buildings located in the 13rd district of Paris were questioned. The social relationships with inhabitants and the satisfaction with spatial comfort in housing are determinant in the comprehension of subjective density in the building (feelings of crowding and crampedness). The implications of these findings for the sustainable development are discussed.