We present data from a group of 636 medical students (School of Medicine, Comenius University in Bratislava). The most frequent used substances are caffeine, alcohol and nicotine. Less frequently used were illicit substances. The most frequent used illicit psycho active substance was marijuana. Using the RCSAST questionnaire we have found a linear association between the number of used drugs / frequency of psycho active substance use and negative effects of the psychoactive substance use on academic performance / student’s life. The results point towards serious negative consequences of regular use of alcohol / regular tobacco smoking, including the higher risk of developing the dependence on these substances. Use of illicit drugs has even more severe consequences than use of legal substances.

Key words: psychoactive substances – medical students – regular use – negative consequences