Psychopathological and cranial computed tomography findings in 48 patients with late paraphrenia were compared with the findings in 40 normal controls. 19 patients with late paraphrenia and first rank symptoms showed significantly less cortical atrophy than 29 patients without first rank symptoms (p less than 0.01). There were no significant differences of ventricular enlargement, cerebellar atrophy, the presence of leukoaraiosis or basal ganglia mineralisation between the late paraphrenic and control groups. In contrast to the controls, cortical atrophy, ventricular enlargement and the presence of leukoaraiosis were not age-related. These results may indicate different origins of late paraphrenia with or without first rank symptoms.