Health services and systems research examines the match between individual and population health needs and clinical services. In the context of the ambulatory shift in psychiatry, services research is important to ensure the quality of clinical developments, their appropriateness to patient and societal needs, their accessibility, efficiency, implementation and real-world outcomes. The purpose of this article is to present the principles that guide mental health services and systems research and to illustrate them with three examples related to the ambulatory shift in psychiatry. Research on services must be based on both epidemiological and clinical research as well as on partnerships with expert patients.