Objective: Underage drinking with increasing pattern towards binge drinking is one of the common problems in European countries. This thesis tries to explain what leads young people to participate in drinking, what is the connection between certain risk behaviours (smoking and drinking) and what role play individuals’ peers in thedrinking habits of adolescent.Method: Econometric analysis is used to identify the determinants of drinking and estimate peer influence on the adolescent. Estimated models are based on the available literature on this topic and on economic theory related to addiction and social interaction. Sample used for the empirical part comes from European School Survey Project on Alcohol and Other Drugs done among high school students in CzechRepublic.Conclusions: Results from the analyses suggest that most common drivers of engagement in drinking are sensitivity on alcohol, friends influence, current smoking status, experience with other drugs and judgment of regular intoxication. Further analysis of causality between drinking and smoking brings evidence that first yearstudents’ smoking and drinking arises from common causes, while for third year students smoking is more attributable to drinking behaviour. Findings from analyses on peer effect show that influence of classmates on the individual varies across genders and its magnitude and significance depends on the estimated sample. Ingeneral, peer effect has always positive sign and regardless of gender and estimated sample it significantly increases participation in drinking of adolescents who have not been drinking before high school.