The radiodensity of the total intracranial area and of the dorsomedial thalamic nuclei were significantly lower in 60 patients with moderate to severe dementia of the Alzheimer type (DAT) compared to 30 healthy age and sex‐matched controls (p<0.02). The radiodensity of the caudate nuclei was similar in the DAT and the coantrol these effects did not exhibit significant correlations with age, duration of illness or global cognitive impairment. The denstitometric parameters discriminated 78.4% of patients and controls; together with the olanimetric measurements 84.4% of the individuals were classified correctly. A potential contribution of white matter shrinkage to ‘cortical atrophy’ and the possible role of thalamic degeneration in DAT are briefly discussed.