Mark Murphy, from The Irish Heart Foundation, refuted the suggestion.
If you can vote at 18 you should be allowed to buy cigarettes.
Speaking on Kildare Today, John Mallon, of the tobacco-funded lobby group Forest Ireland, said 18-year-olds are adults and should be treated as such.
Refuting Mr Mallon's claims, Mark Murphy, from The Irish Heart Foundation, said restricting cigarette sales to 21-year-olds has been shown to reduce smoking rates among teenagers.