ObjectiveCyberbullying involvement carries mental health risks for adolescents, although post-traumatic stress (PTS) symptoms have not received strong attention in the UK. This study aimed to assess the overlap between cyber and traditional (ie, face-to-face) bullying, and the relationship to PTS symptoms in UK adolescents.DesignA cross-sectional survey.SettingFour secondary schools in London,UK.Participants2218 secondary school students (11–19 years).Main outcome measuresThe Olweus Bully/Victim Questionnaire and the Children Revised Impact of Events Scale.ResultsThere was a significant overlap between traditional bullying and cyberbullying. However, cyberperpetrators were less frequently involved in concurrent traditional bullying. Of 2218 pupils, 46% reported a history of any kind of bullying (34% were involved in traditional bullying and 25% in cyberbullying), 17% as victims, 12% as perpetrators, and 4% as both victims and perpetrators. A significant proportion of those who were cybervictims (n=280; 35%), cyberbullies (n=178; 29.2%) or cyberbully-victims (n=77; 28.6%) presented clinically significant PTS symptoms. Cybervictims (both cyber-only and cyberbully-victims) suffered more intrusion (p=0.003; p<0.001) and avoidance (p=0.005; p<0.001) than cyberbullies. However, cyberbullies still suffered more PTS symptoms than the non-involved (intrusion: z=−3.67, p=0.001; avoidance: z=−3.57, p=0.002). Post-traumatic stress symptoms were significantly predicted (R2=13.6) by cyber and traditional victimisation.ConclusionsCyberbullying, as victim only or as a victim-perpetrator, seems to be associated with multiple types of PTS symptoms. Cyber and traditional victimisation significantly predicted intrusion and avoidance. Paediatricians, general practitioners and mental health professionals need to be aware of possible PTS symptoms in young people involved in cyberbullying. Screening and early cost-effective treatments could be implemented.