The purpose of this study was to compare sexual-minority and heterosexual youths' exposure to sexual abuse off-line, problematic sexual meetings off-line with person/s met online and online harassment with regard to prevalence, psychological well-being and support seeking. A nationally representative sample of 3,432 Swedish high school seniors completed an anonymous school-based survey about sexuality, health, sexual abuse and online-related sexual victimisation or harassment. Sexual-minority adolescents reported a greater rate of sexual abuse, problematic sexual meetings off-line with person/s met online and online harassment, compared to heterosexual youth. When compared to non-victimised heterosexual adolescents, victimised heterosexual adolescents and non-victimised and victimised sexual-minority adolescents reported more psychiatric symptoms, lower self-esteem and a weaker sense of coherence. Same-sex sexual orientation was related to more psychiatric symptoms, lower self-esteem and a weaker sense of coherence even when controlled for victimisation and gender. Compared to victimised heterosexual adolescents, victimised sexual-minority adolescents were more likely to seek support because of sexual abuse (females) or Internet-related problems (males and females). Results for sexual-minority youth were basically the same whether sexual orientation was assessed as sexual identity or as sexual or emotional attraction. Health care providers are challenged to not only provide the same care to sexual-minority youth who seek counselling or psychiatric treatment for mental health problems or problems related to victimisation that all adolescents should receive but also to find ways to address topics like prevention of sexual abuse and risk-taking behaviour online or off-line.