This study examined the commonality of exposure to sites that advocate eating disorders, self-injury and suicide among American, British, German and Finnish respondents (N = 3565) aged 15–30 (age M = 23.06, 50.15% male). The analysis focused on both cross-national and socio-demographic differences and on user characteristic including happiness, previous online and offline victimization and online user activity. German respondents had significantly lower levels of exposure to harm-advocating online content than respondents in the three other countries. Females were more likely to be exposed to eating disorder content, while males witnessed more self-injury and suicide content across all four countries. Younger respondents were more likely to be exposed to such material. In addition, other socio-demographic background variables (not living with parents, immigrant background, city residence, online activity) and personal characteristics associated with negative self-schemata were significant predictors of exposure to such content. The findings indicate that those facing difficulties in their everyday life are at higher risk of accessing online sites that may foster unhealthy behavior.