While young people rated Chatroulette, Omegle and Tumblr as high risk for sexual content, parents rated them as low risk - highlighting the need for parents to find out more about these sites.
Peter Wanless, NSPCC CEO, said:
"Our Net Aware research has shown that children are far more likely than parents to report seeing sexual, violent, or other adult content on social media. It's vital that parents sit down together with their children regularly to talk about which social media sites they are using, and how to get help if they need it.
"More than 60% of young people we asked said social media platforms need to do more to keep children safe. These companies need to take more responsibility for keeping children safe online. We think there should be minimum standards in place and a new regulator may be required if industry can not regulate itself.
"Thankfully, it's not all bad news. Around half of the sites in Net Aware have made improvements to their privacy settings and reporting functions - a trend I hope will continue. The NSPCC will continue to campaign for a safer internet, provide support for children through ChildLine, and advise parents through our partnership with O2."
Six new sites have now been added to the Net Aware guide: Dubsmash, Google Hangouts, Steam, Simpsons Tapped Out, YouNow and Roblox2.