Background:Patients with severe mental illnesses (SMI) have low levels of social integration, which could be improved if they used social services. To our knowledge, however, the extent to which they use generic social services remains unknown.Aims:We assessed the extent to which patients with SMI use generic social services and the factors that may drive that usage.Method:In 2014, we carried out a multi-setting clustered survey of patients with severe mental disorders ( n = 1,019, participation rate = 71%) and of services ( n = 517, participation rate = 53%) in 19 networks of services, covering most of Belgium. On the one hand, we asked patients, amongst other, about their health condition, their social integration in the community, and their use of social services of different types. On the other hand, we asked each service to report on its relationships with other services in the services networks.Results:On average, patients’ use of generic social services within the previous 6 months was low (6%–16%), ...