The Iona Institute, which commissioned the research, said almost a third of those surveyed were closer to the figure of 4% of clerics reported in a study by the John Jay College of Criminal Justice in the US.
Iona, which describes itself as a pro-religion organisation, said the poll carried out by Amarach Research reveals that a clear majority of the public overestimate the number of paedophile priests in the Catholic Church.
Professor Patricia Casey, consultant psychiatrist and Iona patron, said: "There has been very deep and completely justified public anger over the scandal of child sex abuse by clergy.
"However, only a small minority of priests are guilty of this terrible crime and in the interests of justice, and in fairness to the vast majority of priests, it is essential that this fact becomes universally known among the public at large."
Iona said the survey found 42% of people put the number of abusive priests above 20% of the clergy.
Prof Casey, a senior psychiatrist at the Mater Hospital in Dublin and a lecturer at UCD, said the extent of the overestimation was worrying.
"It might be understandable if the public were overestimating the number of guilty priests by a factor of two or so," she said.
"But the fact that so many members of the public are grossly overestimating the number of guilty priests should be a matter of deep concern to all fair-minded people."
The findings were based on a nationwide survey of 1,000 Irish people in September using the Amarach Research omnibus service.
Read more: http://www.belfasttelegraph.co.uk/news/local-national/republic-of-ireland/public-overestimates-priest-abuse-16071395.html#ixzz1dCWyqDif