Objective. In absence of a gold standard of methods to assess competence, three judgements of competency of geriatric patients are evaluated: the judgements of a physician, the judgement of a family member, and the judgement of an instrument. Methods. Competence of 80 geriatric patients was judged both by a physician and a family member. Decision making capacity was assessed with a vignette. A vignette describes a treatment choice, after which the following abilities are evaluated: evidencing a choice, understanding, reasoning and appreciating a situation. Cognitive functioning was measured with the Mini-Mental State Examination. Results. Most of the geriatric patients were judged competent by all three methods. Disagreement between the three judgements was found for 25 patients. Agreement about incompetence was only reached for one patient. Physicians appeared to be most lenient in their incompetency judgement: only three patients were judged incompetent. These patients scored significantly lower than competent patients on cognitive functioning, the decisional ability of understanding, and the total vignette score. Family members appeared to be most stringent in their judgement: they considered 22 patients incompetent. Incompetent patients scored significantly lower than competent patients on cognitive functioning, reasoning and the total vignette score. Conclusions. The disagreement between the judgements suggests a difference in factors given emphasis by the three methods. The finding that both the judgement of physicians and family members are associated with the assessment of the vignette, suggests that the vignette method has more than a legal theoretical base and is associated with daily life experience and knowledge as well. Physicians can be helped to assess competence by the vignette method to evaluate decisional abilities and by family members who can provide more information about patients' values.