Cases of drug addicts seeking treatment and rehabilitation have soared by 52% over the last six years, according to research.
Figures released by the Health Research Board (HRB) show the total number of cases seeking help jumped from 5,167 in 2005 to 7,878 last year.
Opiates, such as heroin, were the most common drugs - used by six out of 10 wanting treatment - with 21% addicted to cannabis and 11% hooked on cocaine.
Cannabis was the most common problem drug for new cases in 2010 - overtaking cocaine, which peaked in 2007.
Delphine Bellerose, who wrote the report, said the majority of cases struggled with addictions to more than one drug.
"Over two-thirds of cases had problems with more than one drug, most commonly cannabis, alcohol, cocaine and benzodiazepines," she said.
"The high proportion of cases using multiple problem substances is a challenge for service providers as this group often require repeated episodes of treatment over time."
Data revealed both the incidence (number of new cases) and the prevalence (number of all cases) of treated problem drug use among 15 to 64-year-olds living in Ireland increased consistently.
There were 70 new cases per 100,000 in 2005, up to 106 cases last year, while the prevalence increased from 423 cases per 100,000 in 2005 to 544 cases in 2010.
Drug treatment cases were highest in the South East, followed by the North Dublin and the Southern region.