What role do people want to play in treatment decision-making (DM)? Examine the role patients indicate they would prefer in making treatment decisions across multiple clinical settings in Ontario, Canada. Secondary analysis of a series of survey/interview-based studies measuring preferred role, conducted in 12 different populations. Respondents were outpatients, largely but not entirely attending outpatient clinics in large teaching hospitals in urban settings in the Province of Ontario, Canada. The subgroups and sample sizes were: breast cancer (202), prostate disease (202), fractures (202), continence (46), orthopaedic (111), rheumatology (56), multiple sclerosis (22), HIV/AIDS (431), infertility (454), benign prostatic hyperplasia (678) and cardiac disease (300), plus 50 healthy nursing students (for scale validation). All studies categorized preferred role using the Problem-Solving Decision-Making (PSDM) scale with one or both of the Current Health condition and Chest Pain vignettes. Few respondents preferred an autonomous role (1.2% for the current health condition vignette and 0.7% for the chest pain vignette); most preferred shared DM (77.8% current health condition; 65.1% chest pain) or a passive role (20.3% current health condition; 34.1% chest pain). Familiarity with a clinical condition increases desire for a shared (as opposed to passive) role. Preferences for passive vs. shared roles varied across settings; older and less educated individuals were most likely to prefer passive roles. Despite consumerist rhetoric among some bioethicists, very few respondents wish an autonomous role. Most wish to share DM with their providers.