The number one risk factor for lung cancer is your exposure and exposure to tobacco smoke. The number of cigarettes smoked and the number of years smoked increases the chance of getting lung cancer. People who are more exposed to tobacco, smoke, or smoke from other smokers (secondhand smoke) have an increased chance of getting lung cancer. People who have never smoked may also get lung cancer, but their chances of getting lung cancer are much lower than those who smoke, have smoked in the past, or are frequently exposed to smoke.