Background Risk-based decision making is altered in people with schizophrenia and in people with cannabis use compared to healthy controls; the pattern of risk-assessment in people with co-occurring schizophrenia and cannabis dependence is poorly understood. This study examined measures of risk-taking and decision-making in people with and without schizophrenia and/or cannabis dependence. Methods Participants with schizophrenia (n=24), cannabis dependence (n=23), schizophrenia and co-occurring cannabis dependence (n=18), and healthy controls (n=24) were recruited from the community via advertisements and completed a one-visit battery of symptom, risk-based decision making, gambling behavior, cognitive, and addiction assessments. This report presents self-assessments of self-mastery, optimism, impulsivity, and sensation seeking and a behavioral assessment of risk (Balloon Analog Risk Task [BART]). Results On self-report measures, participants with schizophrenia and co-occurring cannabis dependence were intermediate between those with only cannabis dependence or only schizophrenia on ratings of self-mastery, sensation-seeking, and impulsivity. There were no group differences on ratings of optimism. Their behavior on the BART was most similar to participants with only cannabis dependence or healthy controls, rather than to participants with only schizophrenia. Conclusions People with schizophrenia and co-occurring cannabis dependence may represent a unique group in terms of risk-perception and risk-taking. This has implications for interventions designed to influence health behaviors such as motivational interviewing.