The legal age for smoking could go up from 16 to 18 in England and Wales.
The government is asking people for their opinions on the proposal in a debate that will last three months.
They will also be asked for their views on upping the limit and if there should be bigger punishments for people who sell tobacco to under-age smokers.
It comes after MPs voted to ban smoking in pubs, restaurants and work places from mid-2007. The ban is already in place in Scotland and Ireland.
Research has showed that about 9% of children aged between 11 and 15 smoke.
Launching the debate, a government spokesman said that people who started smoking at a young age were more likely to get hooked for life.
Many campaigners think the current punishments for people who sell to under-age smokers are too soft - with the biggest fine being £3,500.