A study published in the journal Tobacco Control found that smoking in central Delhi was cut by 60 per cent between 2012 and 2014.
The study was carried out by researchers from the Indian Tobacco Research Institute and University of Pennsylvania.
The researchers looked at the relationship between indoor and outdoor smoking in Delhi and compared the results with a previous study in India.
The Delhi study found that, overall, the outdoor smoking rate in the capital fell from 10 per cent in 2012 to 8.6 per cent the next year.
The study also found that the indoor smoking rate fell from 11.9 per cent to 6.7 per cent.
However, indoor smoking was still the leading cause of death in the city, the study found.
The researchers found that about a third of the indoor smokers who died were young adults and were likely to be under-35.