Scientists looked at the effects of six anti-smoking policies introduced in 41 countries, excluding the UK, between 2007 and 2010. Projections of premature deaths likely to be prevented by 2050 produced a figure of 7.4 million.
Increasing taxes on cigarettes to 75% of their price in 14 regions had the biggest impact, which was greater than legal smoking bans.
Tax rises prevented 3.5 million deaths while "smoke-free air laws" in 20 of the countries averted 2.5 million.
The findings, published in the Bulletin of the World Health Organisation, also forecast a total of 700,000 deaths averted by health warnings, 380,000 by cessation treatments, and 306,000 by restrictions on tobacco marketing.