In the nine months before the ban came into force in July 2007 smoking declined by 1.6% compared to 5.5% in the following nine.
It is estimated that at least 400,000 people stopped smoking as a result of the ban.
This could prevent an estimated 40,000 deaths over the next ten years.
Professor Robert West, Cancer Research UK’s director of tobacco studies at University College London’s Health Behaviour Research Centre said: 'I never expected such a dramatic impact.'
The Smoking Toolkit Study, funded by Cancer Research UK, McNeil, Pfizer and GlaxoSmithKline was based on interviews with more than 32,000 people in England.