When patients refuse beneficial treatment, the assessment of decision-making capacity plays a key role in determining the best course of action. However, situations in which patients refuse to explain their reasons occur. This can make an assessment of capacity impossible. In such cases, clinicians find themselves in difficult situations without clear ethical guidance. Refusal to give reasons for refusing beneficial treatment has been seen as pointing to the absence of decision-making capacity. However, the reasons given for this are either unsatisfactory or insufficient to eliminate cases of genuine uncertainty. This article argues that although it cannot be concluded that such patients are incompetent, there are reasons to treat them as if they were. The basis of this possibility, however, points to several obligations for clinicians before such a situation can be said to exist.