Background: This study examined the relationships among cyberbullying, school bullying, and mental health in adolescents. Methods: In 2010, a total of 2992 10th grade students recruited from 26 high schools in Taipei, Taiwan completed questionnaires. Results: More than one third of students had either engaged in cyberbullying or had been the target (cybervictim) of it in the last year. About 18.4% had been cyberbullied (cybervictim); 5.8% had cyberbullied others (cyberbully); 11.2% had both cyberbullied others and been cyberbullied (cyberbully-victim). About 8.2% had been bullied in school (victim); 10.6% had bullied others (bully); and, 5.1% had both bullied others and had been bullied in school (bully-victim). Students with Internet risk behaviors were more likely to be involved in cyberbullying and/or cybervictimization; students who had cyberbullying or victimization experiences also tended to be involved in school bullying/victimization. After controlling for sex, academic performance, and household poverty, cyber/school victims and bully-victims were more likely to have lower self-esteem, and cyber/school victims, bullies and bully-victims were at a greater risk for serious depression. Conclusions: Both cyberbullying and school bullying and/or victimization experiences were independently associated with increased depression. (Contains 4 tables.)