Cyber-bullying: One teenager's experience
18 November 2013 Last updated at 09:00 GMT
Just over a fifth of children have witnessed a classmate or friend bullied online, and only one in 10 parents thinks their child is safe online, research suggests.
But the study from McAfee and the Anti-Bullying Alliance says only a third of those affected by bullying told their parents about the issue.
Graham Satchell met one teenager who was cyber-bullied and now helps others overcome it.