In a woman aged 35 who for the last 5 years had been suffering from conduct disorders, especially kleptomania, compulsive cleaning behaviour and affective neglect of her children, psychodiagnostic examination initially suggested a delusional disorder. In view of the gradual aggravation of bizarre behaviour, the diagnosis 'schizophrenic psychosis of the hebephrenic type' was made; supplementary examination revealed no abnormalities. Finally, in view of the ununderstood and progressive behavioural changes, the diagnosis was reconsidered; on the basis of clinical findings, SPECT examination and results of repeated CT of the brain, the diagnosis of 'frontotemporal dementia, type Pick' was made.