Smoking increases the chance of getting lung cancer, but it is not possible to estimate how many smokers get lung cancer, as the chance of getting lung cancer from smoking is only relative to a normal non-smoker. Some studies have shown that long-term smokers are 16 times more likely to develop lung cancer than non-smokers. If you start smoking before the age of 15, you are 30 times more likely to develop lung cancer. Some studies have also shown that people who smoke a pack of cigarettes a day for more than 30 years are 20-60 times more likely to die from lung cancer than nonsmokers. If the smoking history is 40 years or more, the probability doubles again. The probability of lung cancer from smoking is related to the amount of cigarettes smoked and the age of the smoker, not only smoking, but also passive smoking has a significantly higher chance of lung cancer than normal people.