A ban on the sale of packs of ten cigarettes comes into effect from midnight tonight.
Confectioneries that resemble tobacco products will also be banned.
The Office of Tobacco Control says it hopes the measure will discourage young people from smoking.
Research published last year showed that 76% of young people who smoke buy ten-packs of cigarettes.
Up to 77% of these say they would be likely to quit if cigarette prices doubled.
But a spokesperson for the smokers' rights organisation, Smokers Against Discrimination, said the ban will result in people of all ages smoking more.
John Daly says the only people the ban will benefit are cigarette manufacturers.
One of the world's leading experts on tobacco, who is speaking at a conference in Dublin tomorrow about smoking habits, says cigarette manufacturers deliberately use ten packs to encourage younger people to smoke.
Professor Kenneth Warner says the Irish tobacco industry needs 50 children to start smoking every day to replace the numbers who quit smoking or die from smoking every year.
The ban comes into effect tomorrow but the Department of Health says there will be a period of grace for retailers to allow them to get rid of stocks of ten packs.
After that, anyone who breaches the ban faces a fine of up to €3,000 or up to three months in prison.
