To understand why some adolescents are prone to develop risky behavior online, it is important to specify characteristics that contribute its occurrence and development. The aim of this research was to examine the relation between cyberbullying, generalized problematic Internet use and problematic online gaming with personality traits of the HEXACO model and Dark Triad. Research was conducted on a sample that consisted of 282 high school students in Osijek. Participants completed HEXACO Personality Inventory (Ashton i Lee, 2007), Short Dark Triad (Jones i Paulhus, 2013), Cyberbullying Questionnaire (Šincek, Tomašić Humer, Duvnjak i Milić, 2015), Generalized Problematic Internet Use Scale 2 (Caplan, 2010) and Problematic Online Gaming Questionnaire (Pápay i sur., 2013). Results reveal a significant correlation between personality traits and risky behaviors. Psychopathy was a significant positive predictor of the criterion cyberbullying, while honesty-humility and agreeableness were mediated by psychopathy. Positive predictor of generalized problematic Internet use was emotionality, while honesty-humility, conscientiousness, and extraversion were negative predictors. Dark personality traits did not predict the criterion. Results also indicated that extraversion was significant negative predictors of problematic online gaming while Dark personality traits were not related to the criterion.