Objective. The prevalence of Internet addiction (IA) is growing steadily, especially among the younger generation. The purpose of this multicenter study was to investigate the socio-demographic characteristics, clinical varieties, and profile of psychopathological symptoms of mental disorders in patients with IA. Material and methods. The study included 2 groups: the main group consisted of 44 people, aged 16 to 34 years, average age 22.00±0.66 years, 33 (75%) men, 11 (25%) women; the control group included 120 people, aged 19 to 30 years, average age 23.13±0.18 years, 90 (74.3%) men, 30 (26.7%) women. Groups were identified at the testing stage based on the total score on the Chen Internet Addiction Scale (CIAS). The main group included individuals who scored CIAS 65 points or higher. The specially developed Unified Study Card, The Mini international neuropsychiatric interview (MINI), the Hospital Anxiety and Depression Scale (HADS), the Beck Depression Questionnaire (BDI), the Prodromal Questionnaire-16 (PQ-16), the Symptom Checklist-90-Questionnaire Revised (SCL-90-R). Results and conclusion. There were more people with secondary specialized education and unemployed in the main group. The family burden of addiction and psychiatric disorders did not differ in both groups, and the heredity of somatic diseases was lower in the IA group. In the IA group, a psychiatric diagnosis was made 9 times more often. The severity of affective and anxiety disorders was higher in the IA group, while the risk of psychosis was low that allows considering the symptoms of IA outside the framework of subpsychotic mental disorders. The features of the psychopathological symptoms of IA were: total «tension» of the psychopathological profile; a relatively uniform and slightly specific profile of psychopathological symptoms with a certain tendency to the prevalence of personality-related stress manifestations.