A survey by the Office of Film and Literature Censorship shows nine out of 10 teenagers are consuming restricted films and computer games before they are old enough.
It also found young people want more information on censorship, and the content they are restricted from viewing.
The survey asked 507 people aged 16 to 18 for their views on the classification system.
Just 11% said they never see films or play games with restricted content, and 89% percent have at some point consumed media they were too young for.
The survey also found 33% of those questioned who have siblings or cousins older than them, say they view restricted material often.
But the Chief Censor, Dr Andrew Jack, says those who have younger family members are less likely to view explicit content.
"Young people genuinely care about themselves, their friends, and younger siblings and cousins and use the classifications to help them make decisions around what they let their younger brothers and sisters watch. It's a really interesting phenomenon," he said.
Mr Jack says young people want censor warnings on packaging to be more descriptive.