Nearly 10,000 children told these authors in this report about what upsets them and their friends online. Their responses were diverse, revealing a long list of concerns. Pornography (named by 22% of children who told us of risks) and violent content (18%) top children’s online concerns. Overall, boys appear more bothered by violence than girls, while girls are more concerned with contact-related risks. Violence receives less public attention than sexual material, but many children are concerned about violent, aggressive or gory online content. As children told them, video-sharing websites are often associated with violent and pornographic content, along with a range of other content related risks. Younger children are more concerned about content and other risks. As they get older they become more concerned about conduct and contact risks. These are linked in many children’s minds to the use of social networking sites such as Facebook. Concern about risks is higher among children from ‘high use, high risk’ countries. Policy implications are identified and discussed.