Almost five million people died from smoking-related diseases across the world in 2000, researchers estimate.
Smoking deaths around the world were studied
A study published in The Lancet found that for the first time, deaths from smoking that year were as high in the developing world as in industrialised countries.
Over three-quarters of deaths among smokers worldwide were among men.
Researchers from the Harvard School of Public Health in Boston say the only way to stop deaths increasing is to improve education and prevention work.
They looked at smoking deaths globally, including the developing world, where an estimated 930m of the world's 1.1 billion smokers live.
The researchers estimated that there were 4.83m premature deaths from smoking in 2000 - 2.41m in developing countries and 2.4m in industrialised countries.
In developing countries, 84% of deaths were among men.
Cardiovascular disease was the leading cause of death, killing 1.69m people, followed by chronic obstructive pulmonary disease (970,000) and lung cancer (850,000).
The researchers used US data on deaths from lung cancer as an indication of smoking-related risk, plus data from 125 individual countries.
Cardiovascular disease - 12m a year
Cancer - 6.2m a year
HIV/Aids - 3m a year
TB - 2m a year
Malaria - 1m
Dr Majid Ezzati from Harvard School of Public Health, said an accumulation of the health risks of smoking plus population growth and ageing would mean smoking-related deaths in developing countries would increase over coming decades.
He said: "Mortality as a result of smoking will rise substantially unless effective interventions and policies that curb and reduce smoking among men and prevent increases among women in these countries are implemented."
Amanda Sandford of the campaign group Action on Smoking and Health told BBC News Online there were a number of factors involved in the increase in smoking-related deaths in developing countries.
"Partly it's because in a growing population, so there are more people are smoking.
"But it also stems back to the actions of the tobacco companies,
"They are aggressively marketing their products to developing countries.
"I think we'll be seeing this until the countries themselves put a stop to it."
Ms Sandford added education and prevention measures were essential to reduce smoking-related deaths.