The aims of this study were to determine links between adolescent's well-being and their sexual and romantic activities off- and online. The study includes 245 mid-adolescents (15 years of age; 55 % girls) and 251 late-adolescents (18 years of age; 49 % girls). Of the 496 teenagers, 54 % had experiences of both online and offline sexual and romantic activities, while the remaining (46 %) had only offline experiences.Teenagers' experiences with online sexual/romantic activities were associated with experiences of offline sexual/romantic activities. Multiple regressions showed that age (older) and risk behaviour contributed to higher engagement in offline sexual/romantic activities. In contrast, only higher risk behaviour contributed to higher engagement in online sexual/romantic activities for boys, but for girl several factors, such as age (younger), lower body esteem, higher risk- and problem behaviour contributed to higher engagement in online sexual/romantic activities. We discuss this result from a gender perspective.