Almost three quarters of clients of a Dublin drug rehabilitation programme are drug free after two years, according to a study.
The study of Coolmine Therapeutic Community by Trinity College found that 98% of those who completed the programme had not engaged in criminal activity either.
Coolmine is urging the Government to allow it access to prisons to treat inmates for addiction issues.
Spokesperson Tracey Cagney says treating addicts makes sense.
She said: "Certainly from an economic point of view it makes sense to treat people in addiction.
"From a social point of view, reducing crime, putting people in stable accommodation, having children with their parents and not in addiction.
"From a humanitarian point of view, caring for these people who were all children at one point, their histories of trauma, abuse, poverty, lack of education, lack of employment opportunities - we have a responsibility."