While there is an increasing emphasis on patient empowerment and shared decision making, evidence suggests that many patients do not wish to be involved in decisions about their own care. Previous research has found patient preferences for involvement in decision making to vary with age, socioeconomic status, illness experience, and the gravity of the decision. Furthermore, there is evidence that certain patients may experience disutility from being involved in decision making about the treatment of their health problems. We discuss the implications of these findings for the use of decision support tools and the difficulties of targeting their use towards those patients most likely to benefit. We argue that patients may be ill informed about what participation in decision making actually entails and unaware of the benefits they stand to gain by articulating their preferences to their clinician. Furthermore, clinicians are not good at accurately assessing patients' preferences, while patients may have unrealistic expectations about their clinician's ability to "know what is best" for them. Further research is required to understand variations in patients' preferences for information and involvement in decision making, and the factors that influence them.