Asymmetry of EEG rhythms and intercortical interaction in patients with Major Depression and schizophrenia with negative and positive symptoms were studied by the method of brain mapping. It was shown that in depressive patients the disturbance between anterior and posterior brain areas takes place; in schizophrenics with negative symptoms left hemisphere and in schizophrenics with positive symptoms--right hemisphere are predominantly activated. These inter- and intrahemispheric disturbances correlate with some clinical manifestations of the patients.