Aim. The aim of the study was estimation of the rate of deletion 22q11.2 among psychiatric patients and an attempt at assessment of the degree in which this rate is influenced by coexistence of dismorphic features and congenital defects. Material and methods. Cytogenetic examination was performed in 255 patients with psychosis. Patients were divided into two groups: group I composed of 61 patients with psychosis and at least two phenotypic features characteristic of 22q11.2 deletion syndrome (22q11DS), and group II composed of 194 patients with psychosis without phenotypic features of 22q11DS. Banding and fluorescence in situ hybridization (FISH) techniques were applied. Results. 22q11.2 deletion was found in 3/61 patients of group I (4.9%) and in 3/255 all the psychiatric patients studied (1.2%). This incidence was significantly higher than in the general population (p<0.001). The frequency of the deletion among psychiatric patients revealing phenotypic features of 22q11DS: 3/61 (4.9%) (p<0.0001) was even higher. In all cases with the deletion, the phenotype was characteristic of 22q11DS. Conclusions. Firstly, 22q11.2 deletion was found to be 40 times more common among psychiatric patients than than the general population; sex chromosome aberrations were also significantly more common than in the general population. Secondly, the presence of dysmorphic features and some congenital defects in psychiatric patients increases the rate of 22q11.2 deletion significantly.