Patient decision aids are a means of helping people make informed choices about healthcare that take into account their personal values and preferences. Decision aids are a part of a shared decision making process, encouraging active participation by patients in healthcare decisions.1 2 Decision aids are relevant in many common healthcare decisions. They have been developed to make it easier for patients and healthcare professionals to discuss treatment options. Here, we give an overview of the rationale for the use of patient decision aids, what they contain, the evidence of their efficacy, and examples of their current and potential uses. Shared decision making is a process in which clinicians and patients work together to decide about interventions based on clinical evidence and the patient’s informed preferences.2 It involves the provision of evidence based information about options, benefits, risks, and uncertainties, together with decision support counselling and a system for recording and implementing patients’ informed preferences. There is evidence that patients want to take part in decision making. A recent systematic review of peer reviewed journal articles found that, in 63% of articles most patients expressed a wish to actively participate in decisions around their treatment.3 Also, the wish to participate appears to have increased over time. In studies published before 2000, only around 50% of articles found that most patients wished to be active partners in their treatment decisions, whereas from 2000, the percentage rose to 71%.3 This was especially clear for cancer patients, where most patients in 85% of the 27 studies published since 2000 wished to be involved in treatment decisions. However, patients’ preferences for involvement in decision making are variable and are affected by factors such as age, sex, and education.4 Shared decision making is appropriate for many types of healthcare decisions, …