ABSTRACT Objectives: to investigate the relationship between risk perception and behaviors related to the driving of motor vehicle under the effect of alcohol and/or marijuana of students of a public university between 18 and 29 years; investigating the relationship between driving under influence, students' social network, and driving-related behaviors under the influence of alcohol and/or marijuana. Method: a transversal questionnaire was applied to 383 students. Inferential and descriptive statistics were used for data analysis, processed by SPSS. Results: are students who have used alcohol and marijuana; 37.1% presented problematic use of alcohol and 22.0% of marijuana. Regarding the correlations, the variables related to the use of marijuana were those that presented greater significance. The lower the perceived risk, the greater the possibility of hitchhiking with those who have used marijuana, that is, there is a strong association between taking a ride with someone who has driven under marijuana and the perception of risk of being detected, receiving sanction or suffer any harm (p<0.01). Conclusion: It is clear that in Brazil the emphasis on alcohol use prevention policies should also address issues related to marijuana use and student social networks.