summary A 35-year-old man is suffering from insulin dependent diabetes mellitus, alcohol abuse, an amnestic syndrome and dementia after a hypoglycaemic coma. On two separate occasions a psychiatrist assesses whether the patient is sufficiently competent to give his consent to treatment. The two assessments of competence turn out to be contradictory. It becomes evident that the assessment of competence and the seriousness of the consequences for the patient are deeply intertwined concepts. It is important to keep these two concepts separate and to distinguish clearly between a patient's decision -making capacity and the seriousness of the consequences.