OBJECTIVE:To describe factors associated with self-reported use of emergency contraception in adolescents attending school in the city of Terrassa (Barcelona, Spain) in 2008. METHODS:We carried out a cross-sectional study to describe the health habits of teenage girls and boys attending school in Terrassa. A representative sample of adolescents aged between 14 and 18 years (n=1300) was used. The adolescents were administered a questionnaire designed ad hoc. Adolescents who reported having had sexual intercourse at least once were studied (n=390). The outcome variable was self-reported use of emergency contraception at some time. The explanatory variables provided information on sociodemographic characteristics, drug use and sexuality. The odds ratios (OR) and 95% confidence intervals (95% CI) were fitted using multivariate logistic regression models. The results were stratified by sex. RESULTS:A total of 390 students, 28.2% girls and 20.1% boys (their partners) had used emergency contraception at some time. Among boys, the final multivariate model showed that emergency contraception was associated with alcohol abuse (OR=2.7; 95% CI:1.0-7.5), having sexual intercourse weekly (OR=2.8; 95% CI: 1.1-7.2) and not having discussed issues about sexuality in the classroom (OR=2.5; 95% CI: 1.0-6.5). Among girls, self-reported emergency contraception was associated with alcohol abuse (OR=2.7; 95% CI: 1.4-5.6), cannabis consumption (OR=3.1; 95% CI:1.6-6.0) and weekly sexual intercourse (OR=2.0; 95% CI: 1.1-3.9). CONCLUSION:Promotion and prevention strategies should begin as early as possible. Behavioral differences should be seen from a gender perspective in the fields of both research and program implementation.