How does smoking cause lung cancer?

Doctors believe smoking increases lung cancer by harming the cells that line the lungs. When you inhale cigarette smoke, which contains cancer-causing compounds (carcinogens), changes in lung tissue occur very instantly.

Your body may be able to repair the harm at first. However, the normal cells that line your lungs get further destroyed with each repeated exposure. The damage leads cells to act abnormally over time, and cancer may arise.