This chapter focuses on how patients use health-care services. It addresses screening and medication adherence, vaccination (including COVID-19), and self-management of chronic diseases. The realities of health-care decision-making include both direct and opportunity costs (e.g. time it takes for screening, preparing for screening, side effects).This chapter begins with the biases that influence patients’ decisions about healthcare use including preventative care and self-management. Then, with an understanding of how these biases emerge in many contexts, the chapter discusses tools from behavioural economics that could help. Finally, the chapter goes through several examples where we know something about how behavioural economics can help (or not!).