The aim of the paper was to establish the type of mental disorders resulting in hospitalization of young people who had used certain psychoactive substances (PS). An analysis of medical records of all patients hospitalized during a year (1999-2000) at the Youth Psychiatry Department indicated that 42 patients in the age range 15 to 23 had used PS for at least a month and that according to ICD-10 criteria either harmful substance use or substance dependence syndrome were diagnosed in their case. Among youth hospitalized for mental disorders 21% had used psychoactive substances for over a month, most often cannabis (in over 2/3 of cases). Over a half of the cannabis users reported their using other psychoactive substances as well, usually alcohol. Young patients hospitalized for mental disorders who had used volatile solvents and opiates did not confirm their using other psychoactive substances. Among young patients hospitalized for mental disorders and using various psychoactive substances in the past most often psychotic disorders were diagnosed, with predomination of these from the schizophrenia spectrum (the latter occurred in this, category of patients almost 4 times more frequently than in the population of all patients).