A third of sunbed salons are knowingly allowing under 18s to tan.
The Irish Cancer Society carried out a mystery shopper survey which found that two out of five operators are not asking for ID.
Sunbed businesses are legally prohibited from allowing minors to use their facilities.
Averil Power, Chief Executive of the Irish Cancer Society said: "Sunbed legislation is there to protect young people who are at the highest risk of developing skin cancer.”
“It is also alarming so many adults continue to use sunbeds regularly given the clear link with skin cancer. Almost 12,000 people get skin cancer in Ireland each year, more than any other cancer. 1,110 of those are diagnosed with melanoma, the deadliest form of the disease.”
There is a 75% increased risk in melanoma when people begin tanning regularly before the age of 35.
The survey carried out by Ipsos MRBI across 40 tanning and beauty salons in Dublin, also showed that one in four sunbed operators offered free sunbed minutes and one in five used two-for-one promotional offers, which the society says are in clear breach of sunbed legislation.
Ms. Power said: “The Irish Cancer Society is concerned to see operators flouting sunbed legislation. They’ve had almost five years to comply and need to get their act together.”