Officers in Cumbria are warning parents to be alert to signs of internet bullying over the summer holidays and to learn more about what their children are doing online.
Online threats are the biggest risk, but the police are also concerned about an increase in teenagers texting pornographic images.
The warning came as the Prime Minister said Britain had to do more to protect childhood innocence.
Dan Ashby reports:
Cumbria Police is urging parents to be aware of a potential surge in internet bullying over the school holidays, as children spend more time on computers.
The force is encouraging parents to engage with what their children are doing online and give them as much help and guidance as possible.
Connor Strange was bullied online for four years and told ITV News Border that it had "a massive effect" on him.
He says he was traumatised by threatening messages which wished death upon him.
Cumbria Constabulary is warning children about the dangers of the internet, as school holidays begin.
The force is highlighting the problems of bullying and fraud, as well as so-called 'sexting' - which is where mobile phone users send naked pictures via text message.