This paper highlights some of the limitations of models of patient involvement in decision-making and explores the reasons for, and implications of, these limitations. Taking the three models of interpretative, shared and informed decision-making as examples, we focus on two limitations of the models: (1) neglect of which decisions the patient should be involved in (the framing problem) and (2) how the patient should be involved in decision-making (the nature of reasoning problem). Although there will inevitably be a gap between models and practice--this much is in the nature of the models--we suggest that these two issues are substantially neglected by the models and yet are fundamental to understanding patient-doctor decision-making. We also suggest that the fundamental problem that lies behind these limitations is insufficient attention to, and explicitness about, the dilemmas of professional ethics, which are played out in the professional-patient relationships that the models are supposed to represent, particularly with respect to the issue of expert and lay accountability.