Study Objective: To assess initiation of sexual activity and contraception methods used among Greek adolescents. To determine the association of adolescents' emotional and behavioral status with their sexual activity. Design: A descriptive cross-sectional survey was conducted. Setting, Participants: The population (N = 1074, age 14-16) consisted of a random sample, stratified according to locality and population density, of 20 public junior high and high schools located in the urban district of Athens, Greece. Interventions: Anonymous self-reported questionnaires were used to assess sexual activity choices and contraception methods. The Youth Self-Report questionnaire was used to evaluate the psychosocial competencies and difficulties of Greek adolescents. Measures: Analyses included frequencies with chi-square tests and multivariate logistic regression analysis. Main Outcome: Factors that may influence sexual engagement of Greek adolescents were assessed. Results: Of the adolescents who completed the questionnaire 21.8% reported having experienced sexual intercourse. The male/female ratio was 3/1 (P < .001) and the mean age of sexual debut was 14.5 +/- 0.9 years. Condoms were the most preferred contraceptive method (79.9%), followed by withdrawal (38.9%). Emergency contraception was used by 9.6% of participants. Adolescents with separated, divorced or with a deceased parent, and non-Greek nationality have higher possibility of being sexually active. Adolescents who reported sexual intercourse had significantly higher score of thought problems (beta = 1.07, SE = 0.35, P = .002), attention difficulties (beta = 0.67, SE = 0.29, P = .022), delinquent behavior problems (beta = 2.37, SE = 0.34, P < .001), aggressive behavior (beta = 1.97, SE = 0.48, P < .001), and externalizing problems (beta = 4.18, SE = 0.78, P < .001). Conclusions: Engagement in sexual activities was significantly associated with psychosocial difficulties among adolescents living in Greece.