THEY cost up to $20 a packet, carry stomach-churning health warnings and have become so socially unpalatable, retailers are forced to keep them under the counter.

So, in a country with some of the world's toughest tobacco laws, who still smokes cigarettes? And with 40 years of quit campaigns highlighting the catastrophic health risks, why do they continue to light up?

Australian adult smoking rates are at an all-time low of around 17 per cent, down from 34 per cent in 1980, making our success in tobacco reform the envy of the world.

But it has left some public health experts wondering if they've achieved all they can in the fight to stub out smoking. Those who still smoke, they say, are predominantly either young experimenters or the severely addicted.

"There's a small percentage of people who have decided, 'well bugger it, I enjoy it, I'm going to take the risk and hope all those terrible things don't happen to me' but they're a pretty small minority. Most people are pretty heavily addicted. They are genuinely trapped," Professor Ron Borland, senior researcher with the Cancer Council Victoria, told The Sunday Age. "We've done research that shows people under 30 tend to say, 'well I'll quit before I'm 30' and people over 40 say, 'well I've got this far and I seem ok, therefore I'm going to be one of the lucky ones.' It's very hard to imagine having lung cancer at the age of 29 and it's fairly unlikely you'll have a heart attack in your 30s. That's part of the reason it's easy to keep on smoking."

While the highest smoking prevalence remains among young people — 21 per cent of 20 to 29-year-olds smoke daily — over time, less are taking up the habit. In 2001, 28 per cent in this age group smoked.

Morgan Reynolds, a 29-year-old complaints investigator for the telecommunications industry ombudsman, started smoking at 18 and has tried to quit twice, the longest stretch lasting three years.

"I probably smoke about 10 to 15 cigarettes a day. On a night out it would be double that but I smoke less now that you can't smoke in pubs," he said. Growing up his older brother smoked and his parents are also former smokers.

Leading tobacco reform campaigner Professor Simon Chapman said being raised in a family of smokers is one of the biggest determinants of future smoking, along with low socioeconomic status.

He said it was a myth that more women smoked than men, with latest figures showing 15 per cent of Australian women smoke daily, compared to 18 per cent of men.