The literature provides information on the high prevalence of periodontal diseases and hard tooth tissues in patients in a psychiatric hospital. The relationship between periodontal microbiota and psychiatric pathology and the need to maintain oral health among this group of patients is discussed. The aim of the investigation was the study of the structure of periodontal diseases in patients of a psychiatric hospital, in various age groups. Material and methods of research. In the Republican Clinical Psychiatric Hospital named after V.N. Bekhterev (Kazan) in the period from 2014 to 2018, 200 patients (95 women and 105 men) aged 35 to 65 years (average age 56,26 ± 6,74) were examined. The questionnaire recorded the patient's age, sex, diagnosis of the underlying disease, dental formula, a standard periodontal diagram was filled in. The maximum depth of the periodontal pocket was determined by sequential measurements. The results of the study. In 100% of patients in a psychiatric hospital, periodontal tissue damage was detected, of which 86.5% in the form of chronic periodontitis. The maximum number of patients with periodontitis was detected in the age group of 51–60 years. The largest number of teeth removed in patients over 70 years of age. There was a direct strong correlation between age and the number of teeth removed (rp = 0.923; p < 0.001). The maximum depth of the periodontal pocket was also in the age group of 51–60 years and amounted to 4,25 ± 1,14 mm. A direct strong correlation of the depth of the periodontal pocket with the number of teeth removed was revealed. The deeper the patient has pathological pockets, the more teeth are removed (rp = 0.892). Conclusions. The results of the study suggest the need to develop training programs for patients and psychiatric hospital staff to improve the quality of life of patients and general health.