Lung cancer is the most common form of cancer caused by smoking. More than 80% of cases of lung cancer are due to smoking.Cigarette smoke contains many chemicals that interfere with the body's method of filtering air and cleaning out the lungs. The smoke irritates the lungs and leads to overproduction of mucus.ong term exposure of the lungs to the irritants in tobacco smoke destroys the normal lung structure. The elastic walls of the small airways within the lungs are broken down. This reduces the amount of lung tissue available for the transfer of oxygen from the air to the blood.