Homeless and drugs services charity Merchants Quay Ireland provided support to almost 9,500 people last year, an increase of 9% on 2008.
The charity said there had also been an increase in the number of people using its homeless services. In the first six months of this year, demand was up by 16%.
Merchants Quay Ireland is now delivering services in 11 counties, reflecting, it says, that the drugs crisis "is a national crisis".
Heroin use continues to be a serious problem, with 642 new injectors presenting to the Merchants Quay service in Dublin last year.
There was also a sharp rise in the number of people seeking support from the charity in the Midlands.
The charity says there is now a significant problem with heroin and cocaine use in Athlone, Portlaoise, Birr and Longford.
The number of prisoners seeking addiction counselling services exceeded 1,000 for the first time.