The latest class of graduates of the drug treatment unit - a therapeutic community environment where prisoners are encouraged to speak freely about their addiction - was significant as it was the 75th graduation.
Programme facilitator and CareNZ chief operating officer Gill Hood said it was great to see the impact the programme had on people's lives.
"Overcoming addiction requires a strong determination to change.
"In the end it's not only the men who benefit but also their whanau and the wider community,'' Ms Hood said.
The drug treatment unit housed up to 45 prisoners in a separate area inside the prison walls.
Methamphetamine, alcohol and cannabis addictions were the most common among prisoners passing through the unit.
OCF prison director Jack Harrison said it was a "big deal'' for the programme.
"By tackling alcohol abuse, we're giving people a better shot at a better life,'' he said.
Only 10% of prisoners who passed through the treatment unit returned, but that did not mean most were being rehabilitated.
A prisoner and graduate of the programme, who could not be named, said the unit had helped him "restore faith in himself'' and learn coping strategies, which he "severely needed''.
