Two in every five tanning salons in Dublin let under eighteens use sunbeds.
A mystery shopper exercise also found many of them are still offering free minutes, which are banned by law.
Laws banning sunbed businesses from letting minors use beds were introduced 5 years ago.
As part of this check, The Irish Cancer Society sent 16 and 17 year olds to 40 tanning salons to see if they could make an appointment.
Two in every five they went to didn't ask their age or for ID.
Many of them are also still running banned promotions.
Averil Power, Chief Executive of the Irish Cancer Society, explained they are things like:
"Free minutes, happy hours, two-for-one offers".
Professor Anne Marie Tobin, a skin expert, says using beds when you're younger is extremely damaging:
"UV exposure at a young age is much more risk than exposure you get later in life".
"Stopping later on is irrelevant", she said.
Almost 12,000 people get skin cancer in Ireland each year.
Those who tan regularly before the age of 35 increase their risk of developing melanoma by 75%.
