Nearly one in three kids aren't taught about staying safe online, according to new research out on Wednesday.
The study also found that kids who know more about using the internet are actually most at risk from things like bullying and unsuitable sites.
Professor Sonia Livingstone, who led the research, said the biggest danger was from giving out personal details and meeting people from chat rooms.
She added more should be done to make the web a safer place for children.
That included schools, the government and internet companies taking steps to keep kids away from danger.
Professor Livingstone told Newsround that lots of kids weren't taught why the internet could be dangerous, and weren't aware of the risks of things like instant messaging.
She added: "Restricting children's internet use reduces the risks, but also carries a cost because it reduces their opportunities online."