Many teenagers who have experienced online bullying are choosing to keep it to themselves rather than tell someone about it.
According to a survey by Opinium for Knowthenet.org, only 37% reported the abuse to the social network they had experienced it through.
Over a third of those deciding not to report the incident said it was because they felt no action would be taken.
Fewer than one in five teens (17%) said their first reaction would be to tell a parent. Just 1% said telling a teacher would be their first response.
Those most likely to be the victims of online bullying or trolling were 19-year-old boys. In this age group, 85% said they had experienced it - 10% more than girls of the same age.
Arthur Cassidy, media psychologist and Knowthenet trolling expert said: "Whilst some might expect girls to be more vulnerable online, this study shows that older boys are more at risk from trolling and cyber bullying.
"Many boys feel under pressure to demonstrate their bravado, particularly on the web, but this attitude and male deficiency in coping strategies can make them more vulnerable and open to trolling.
"Online bullying can have a massive impact on older male teenagers at a time when they are finding their identities.
"Suicide rates are particularly high amongst this demographic, so it's worrying to hear that teenagers on the whole are choosing to deal with internet abuse themselves rather than speaking to parents or teachers for help."
Overall, just under two thirds of teenagers (65%) said they had been affected by online bullying or trolling. For a third (34%), it had lasted more than a month.
A majority of the victims (87%) said they had experienced it on Facebook. This was followed by:
• Twitter 19%
• Blackberry Messenger 13%
• Ask.fm 9%
• Bebo 8%
• Whatsapp 4%
By comparison, the survey found that far fewer teenagers were experiencing offline bullying (49%).
Knowthenet's Phil Kingsland said: "Parents may find it frustrating that children spend so much time absorbed with their smartphone or on social networks. It's precisely because of the importance of these networks to youngsters that they can also cause great distress.
"Understanding the potential impact trolls can have on teenagers is the first step to engaging with your youngsters about this, and helping them to deal with these issues.
"Online trolling can be as traumatic as physical bullying in the playground, so it's important that action is taken quickly and parents and teachers work together to monitor and deal with the issue."
Emma-Jane Cross, chief executive and founder of the charity BeatBullying commented: "Bullying both on and offline continues to be a serious problem for a huge number of teenagers and we cannot ignore its often devastating and tragic effects.
"We work with hundreds of young people being cyber-bullied or trolled so badly that it can lead to depression, truancy, self-harm, or even force them to contemplate or attempt suicide. What's also concerning is that many young people could be suffering in silence.
"The most important thing for young people to remember is not to ignore it. If you see cyber-bullying going on, report it to the site concerned and offer your support. If you're being cyber-bullied, always save any bullying messages, posts, pictures or videos you receive or see.
"Never respond or retaliate, as this can just make things worse, and block any users that send you nasty messages."
The top three tips from Knowthenet.org.uk to tackle online trolling are:
1. Don't feed the trolls – trolls feed off your response so whatever you do, never reply.
2. Tell a mate, a teacher, a parent or someone you trust about it as soon as possible.
3. Collect evidence of email or message trails in case it gets more serious.
1. Listen to your teenager and discuss the problem they're having.
2. Help your child with the practical elements of gathering evidence but be respectful of their privacy so so ask before reading their messages
3. Support your child in reporting the abuse to the social network, online messaging service, or even the authorities and keep monitoring the situation on a regular basis.