Over one in six motorists who were tested for drug-driving have failed a road-side test so far this year.
The latest figures from Gardai found 384 people have been caught driving under the influence of illegal drugs this year.
Five out of six motorists who failed a random road-side test in Dublin at the weekend were under the influence of drugs.
New Road Safety Authority figures found just over two thirds of motorists caught under the influence of drugs had cannabis in their system.
They were released as part of the first day of Road Safety Week.
The Medical Bureau of Road Safety (MBRS) findings also demonstrate that cannabis is now not far behind alcohol in blood and urine samples it examined.
Moyagh Murdock is chief executive of the RSA:
"The analysis presented today, are starting to give us a clearer understanding of the prevalence of drug driving in Ireland.
"It's concerning, because they confirm that drug driving is a major problem on our roads.
"We will continue to educate drivers on the dangers of driving under the influence of drugs."
The research also found that 86% of those who failed a road-side test for drugs were men.