This study examined the associations between sexual orientation of young people and their health and risk behaviours in Thailand and Sweden, and to explore similarities and differences between the countries.A cross-sectional study using data from the Life and Health - Young surveys in Thailand and Sweden. Three different statistical analyses were used to examine the associations of the variables.In total, 3869 students aged 16-18 years old were included: 1488 Thai students and 2381 Swedish students. Significantly more Thai (20%) than Swedish (9%) students identified themselves as bisexual, homosexual or unsure (p < .001). Bivariate analysis showed that, in Thailand, self-harm was more often reported by the homosexual, unsure, and bisexual groups than by the heterosexual group (p = .005). In Sweden, early sexual debut was more often reported by the unsure, bisexual, and homosexual groups than by the heterosexual group (p = .033). Multiple logistic regression analysis showed that homosexual and unsure sexual orientations were significantly associated with self-harm (p < .05) among Thai students. Unsure sexual orientation was significantly associated with early sexual debut (p = .04) among Swedish students. Multiple correspondence analysis indicated that sexual orientation was associated with health and risk behaviours, and varied by different subcategories of students' backgrounds such as country, sexual orientation, family structure and adult support.Sexual minority young people reported more risk behaviours and poorer health than their heterosexual counterparts. The findings are useful for policy programmes on sexual and reproductive health and rights of young people.