Women smokers were compared to men
Women who smoke are no more likely to develop lung cancer than men, US researchers have concluded.
There had been conflicting evidence on women's risk, but the National Cancer Institute study of over 450,000 people found no gender difference.
The study published in Lancet Oncology found a difference of only 0.9% between the risk for men and that for women.
The most recent UK statistics show that in 2006, 23% of men and 21% of women were cigarette smokers.
Lung cancer kills around 30,000 people a year in the UK.
'Vigorous efforts needed'
The researchers analysed data on smoking habits, diet, exercise and alcohol use for 279,214 men and 184,623 women aged between 50 and 71 living in eight US states.
They then looked at lung cancer rates.
The difference in risk for women and men who smoked was just 0.9%.
Men and women who smoke more than two packs per day were about 50 times more likely to develop lung cancer than people who had never smoked.
The team, led by Dr Neal Freedman, said their study benefited from its size, giving reliable findings
They conclude: "Our findings suggest that women are not more susceptible than men to the carcinogenic effects of cigarette smoking in the lung.
"Vigorous efforts should continue to be directed at eliminating smoking in both sexes."
Andy McEwen, assistant director of tobacco studies at Cancer Research UK's Health Behaviour Research Centre, said: "Smoking has a devastating effect on the health of people trapped by their tobacco addiction.
"The risk of a smoker, male or female, developing lung cancer is 15 times greater than that of a non-smoker and smoking continues to be the biggest preventable cause of death for men and women."
"Smoking accounts for the vast majority of cases of lung cancer worldwide.
"More has to be done to help all smokers to quit if we are to prevent future deaths from lung cancer."