"Based on the latest official statistics of the committee to combat narcotics, the number of drug addicts is 1.2 million," a director of the committee, Houman Narenjiha, was quoted as saying.
"The average age of the addicts is 32," he said, adding the average age at which the victims took to drugs was around 23.
Narenjiha did not specify the drugs, but such statistics usually refer to opium and heroin users.
Iranian authorities admit the country has a serious drug abuse problem.
Iran's health ministry says intravenous drug use is the main cause of infection of HIV patients, estimating that it accounts for 77.5 percent of the total of a least 19,435 people who are infected with the virus.
Iran is situated along one of the main trafficking routes for cannabis, heroin, opium and morphine produced in Afghanistan, and designer drugs have also found their way into the local market in recent years.
Iran's police said in April that 7,700 tonnes of opium was produced in Afghanistan in 2008, of which 3,000 tonnes entered Iran, adding that the force had managed to seize 1,000 tonnes of the smuggled opium.
Iran has close ethnic and religious ties with Afghanistan, but the Islamic republic has suffered badly from the effects of surging opium production there, as cheap and readily available heroin has fuelled a sharp rise in drug use.
