The purpose of this article is to determine the differences and similarities between adolescents from Barcelona and Bogotá in their psychoactive substance use habits, their perception of the activities that involve this use and how their risk perception can influence these habits. The sample consists of 865 school students from both cities, with ages between 15 and 18 years. Risk perception was assessed using the risk variables studied by Benthin, Slovic and Severson (1993). Substance use habits were assessed on the basis of the answers given by the youngsters to questions on the age when they first used any substance, frequency of use in the last week and use intentions in the next year. The findings suggest that the age they begin to use alcohol and marijuana and the first time they get drunk differ significantly between the adolescents in the two cities. The Barcelona youngsters have a higher tendency and actual use in respect of all the substances studied than the Bogotá youngsters. Perceived pleasure or benefits predict an increase in both the intention and frequency of use for almost every substance in this study for all, with the exception of the older adolescents (17 to 18 year-olds) from Bogotá. Fear of the consequences or the perception of a risk of illness or injury and conditions favouring use do not seem to have an obvious influence on the various use habits. Key words: Substance