Researchers have a piece of advice for governments who want to help smokers kick 'butts'; keep all warnings printed on cigarette packages as graphic and as big as possible.
The UN's World Health Organization (WHO) identifies smoking as the second major cause of death in the world.
It is responsible for the death of one in 10 adults worldwide, or about five million deaths each year.
The researchers led by David Hammond, Ph.D., of Canada's University of Waterloo analyzed smoking prohibitory messages on cigarette packets marketed in Canada, Australia, Britain and U.S during the period 2002 to 2005.
The researchers quizzed around 15,000 smokers on how effective these messages were in alerting them to the dangers of smoking and in helping them quit.
The results published in American Journal of Preventive Medicine seek to encourage governments to pay attention to the way these messages are displayed as they had a bigger impact than expected.
In Canada highest response or awareness to these messages was recorded. Sixty percent of those questioned said there were alerted to the ills of smoking by these messages. Here the ads printed on the cigarette packet were large colorful graphic representations such as a drooping cigarette indicating impotence, a rotting mouth -indicative of gum disease, mouth cancer etc.
Next came Britain, which introduced large text messages on the front of the packet and smaller warnings on the side. This was in 2003, when the study was being carried out.
Before the new messages were introduced, only 44 percent of British smokers said they were aware of packet warnings. Afterwards, the awareness rose to 82 percent, a sign that bigger messages and new messages are vital, according to the researchers.
In Australia text messages covered more than a quarter of the pack, and an awareness of 52 percent was recorded.
Awareness among Americans was dismally low at 32 percent. Here there was a warning from the U.S surgeon-general given as a small text message printed on the side of the cigarette packet. Incidentally, this message has remained unchanged since 1984.
Researchers also reported a direct link between willingness to quit and ad size and type.
In Canada and Britain, more than 10 percent said the labels had stopped them from reaching for a cigarette at some point in the past six months, and nearly 40 percent said the warnings had prompted them to think about giving up smoking in the previous month.
In the US, those figures were around seven percent and about 25 percent respectively.
In response to the study, Professor Gerard Hastings, of the Institute of Social Marketing at the University of Stirling, says: "We know health warnings work and can save lives as a result. But this study shows that the design and freshness of the message affects how well it does its job."
Some other countries get even more graphic with their warning labels, according to the report. For instance, a Thai label includes a picture of a man smoking, with skulls floating in the background. A Brazilian label shows an unhappy couple in bed, with a warning about impotence from smoking.
Another label image proposed by the European Union is a drawing of a dead man, his eyes covered by a cloth, lying on a table. The words "Smokers die younger" appear next to that image.
Similar research funded by Cancer Research UK has found that prominent warnings were more likely to be read but they must also be updated regularly or smokers became resistant to them.