Lung cancer is a type of cancer that begins in the lungs. Your lungs take in oxygen when you inhale and release carbon dioxide when you exhale.
People who smoke are at a greater risk of getting lung cancer, though lung cancer can also occur in people who have never smoked. The risk of lung cancer increases with the length of time and number of cigarettes you've smoked. If you quit smoking, even after smoking for many years, you can significantly reduce your chances of developing lung cancer.