Competence is central to informed consent and, therefore, to medical practice. In this context, competence is regarded as synonymous with decision-making capacity. There is wide consensus that competence should be approached conceptually by identifying the abilities needed for decision-making capacity. Incompetence, then, is understood as a condition in which certain abilities relevant to decisionmaking capacity are lacking. This approach has been helpful both in theory and practice. There is, however, another approach to incompetence, namely to relate it to mental disorder. This approach has been followed in recent research that has shown, for instance, that in anorexia nervosa a person's values may be changed, resulting in 'pathological' values. We explore some advantages and disadvantages of both abilities-based and pathology-based approaches. We argue that both can be valuable for further clarification of the concept of competence and improving clinical practice. Given the current predominance of the abilities-based approach, we make a plea for a greater focus on pathology-based practice and research.