Background: Few studies have considered the impact of demographic and clinical variables on help received respectively from services and relatives to satisfy needs of adults with severe mental disorders (SMD). Purposes: To identify major needs receiving help and, using the Andersen’s Behavioural Model of Health Service Use, to identify and compare predisposing, enabling and need factors associated with help given respectively by services and relatives. Methods: 352 adults with SMD from Montreal (Canada) were interviewed using six standardized instruments. Clinical records were consulted. Multiple linear regression analyses were processed to measure level of help received from relatives and services. Results: Factors significantly associated with help from relatives were: higher number of perceived needs; fewer diagnoses; better community functioning; being younger, and in a conjugal relationship; living autonomously; having social support and better quality of life; and, marginally, being an immigrant. Factors significantly associated with help from services were: higher number of perceived needs, better quality of life, supervised housing, adjustment disorder and schizophrenia. Conclusions: Help overall is insufficient to meet users’ needs. Services are more helpful than relatives, in particular regarding health needs. Comparatively to help from services, help from relatives is associated with predisposing factors like age, marital status and nationality.