Some 40% of children aged between eight and 10 are talking to strangers online.
That's according to figures released on Safer Internet Day by CyberSafeIreland.
They show 79% of these children own a smart device capable of giving them access to the internet.
Almost one-third of them are speaking to strangers every day or at least once a week.
While almost one-quarter are also playing over-18s video games, containing violent or sexually inappropriate content.
The survey found that 10% are online for more than four hours every day - and that more than one-third rarely or never talk to their parents about online safety.
CyberSafeIreland is highlighting the importance of parents engaging in their children's online lives, in order to protect them from risk.
They surveyed 1,200 children aged between eight and 10 in schools between September and December 2018.