The government is launching a campaign to highlight the forthcoming rise in the legal minimum age at which tobacco can be bought in England and Wales.
The move is designed to cut teenage smoking rates
A website is going live, and this will be accompanied by a mass mailing to 100,000 retailers and online advertising aimed at teenagers.
From October 1, the minimum age will increase from 16 to 18 years in a bid to cut the number of young smokers.
It comes after the recent introduction of a ban on smoking in public places.
About 9% of 11 to 15-year-olds smoke, and ministers hope the forthcoming move will reduce this figure.
The government argues that raising the legal age to 18 will make it easier for retailers to spot under-age smokers.
Ministers believe that bringing the age for the purchase of tobacco into line with that of alcohol will reinforce the dangers of smoking to young people.
It will also bring England and Wales into line with Canada, Australia, New Zealand and the US.
Research has suggested that only a quarter of children aged under 16 who tried to buy tobacco found it difficult to do so.
The campaign will also promote the stop smoking services which are on hand.
Public Health Minister Dawn Primarolo said: "Currently, half of all teenagers who smoke will die from diseases caused by tobacco if they continue to smoke throughout the course of their life.
"Raising the minimum age at which teenagers can be sold tobacco products will reduce the availability of cigarettes, and could therefore discourage young people from taking up smoking in the first place."
Retailers that stock tobacco will have a legal obligation not to sell to under 18s and will risk prosecution and a fine of up to £2,500 if they do so.
Association of Convenience Stores chief executive James Lowman, said: "Retailers will be the front line defence against under 18s buying tobacco and this campaign will help them to do this job."
Maura Gillespie, of the British Heart Foundation, said raising the legal age "sends out a clear message".
But she added: "There are still a number of supporting initiatives we would like to see introduced to make smoking less attractive and cigarettes less available.
"These include closing the loophole that currently allows manufacturers the opportunity to advertise at the point of sale, and a total ban on selling cigarettes in vending machines."