The study aimed at searching for mechanisms of communicative impairments in patients with schizophrenia and their relatives. To evaluate a contribution of attention and memory to communication efficacy and to ability for understanding mental states of others, 100 patients with schizophrenia and schizoaffective psychosis, 150 their healthy relatives and 145 controls have been studied. The results confirmed a presence of communicative deviations in the patients with schizophrenia and their relatives. In these groups, communication deficit was determined by disturbance of 1 out of 4 communication principles--the principle of information quantity. Attention and memory did not exert any significant influence on communication efficacy in the patients and their relatives. Distinct deterioration of fulfilling the tasks demanding mentalizing ability was found only in the patients. However, no correlation was revealed between this deterioration and communication peculiarities.