The co-presence and cohabitation relations in HLM projects with differentiated populations on the basis of their ethnic or racial origin raise the question of the compatibility of some behaviors (modes d'habiter ) of the groups sharing the same daily environment. If these behaviors are much contrasted, the cohabitation relations could create tensions or conflicts and encourage some attempts to appropriate exclusively one project by a group. We will focus on these situations. After a short exam of the objects of conflict, we will show how the representation of other groups by one group is constructed through a process that we name ethnicisation of differences. The calling into question of the universal character of the behavior of the majority group induce a strong feeling of desappropriation experienced by this group. This situation leads to the emergence of territorial conflicts which necessitate the implementation of a new mode of management of the relations between inhabitants. This mode of management should permit the emergence of a new territoriality constructed on bases other than ethnic homogeneity and should be able to integrate diversity.