BACKGROUND People with serious mental illness (SMI) often suffer high healthcare costs and enduring loss of quality of life. Increasing our understanding of the cost-effectiveness of people with SMI is important when striving for optimal health at affordable costs. AIM To describe aspects that can be important for cost-effectiveness research targeting people with SMI. METHOD These aspects are demonstrated by considering pro-active care, rehabilitation and involuntary treatment RESULTS The possible involvement of a large number of stakeholders outside of healthcare requires cost-effectiveness research to also map the costs and benefits outside of healthcare, preferably for each stakeholder specifically. Availability of data, the possibility ...