This study explores the prevalence and predictors of three sexual contact and conduct risks through mobile phone use among adolescents (N = 540): (1) the exchange of sexually explicit content, (2) the sharing of one's mobile phone number with a stranger from the opposite sex, and (3) participation in anonymous chat rooms on TV. One in three adolescents admits having exchanged sexual content, one in five reports having shared their number with a stranger, and one in ten has participated in TV chat rooms. Contextual predictors were gender, age, having a (romantic) partner, self-esteem, popularity, susceptibility to peer pressure, parent attachment and attitude towards school. Strong mobile phone use predictors were the frequency of text messaging, problematic phone use and using one's phone to avoid face-to-face interactions. However, different patterns emerged for the different mobile phone practices and for girls and boys, indicating the need for further research.