Lung cancer is a cancer that starts in the lungs. The major cause of lung cancer is smoking cigarettes. But people who don’t smoke may get lung cancer, too. Learn about risks you might have for lung cancer by taking this assessment. A risk factor is anything that affects your chance of getting a disease such as cancer. Having a risk factor, or even several risk factors, does not mean that you will get the disease. And some people who get the disease may not have had any known risk factors.