The aim of the reported study was to assess the MMSE and some other neuropsychological tests scores in the diagnosis of cognitive deficits in patients with either psychotic disorders or confirmed brain damage without clinically manifested dementia. Subjects in the study were 44 patients with mental disorders in remission and 37 patients with the CNS lesions. No significant differences between the two groups were found on the MMSE, although performance of patients with bipolar affective disorder was better than that of patients with encephalopathy. Schizophrenic patients had considerable difficulties with learning new material. Administration of a battery of neuropsychological tests may contribute to a more precise differential diagnosis in some specific cases only, but the tests may be useful in the assessment of adjustment ability in patients with psychotic disorders.