The mutations that lead to lung cancer had been considered to be permanent, and to persist even after quitting. But the surprise findings, published in Nature, show the few cells that escape damage can repair the lungs. The effect has been seen even in patients who had smoked a pack a day for 40 years before giving up.
Can Lungs Go Back to Normal After Quitting Smoking? Yes, your lungs can go back to normal after quitting smoking. One large study found that after 20 years smoke-free, the risk of COPD drops to the same as if you have never smoked and after 30 years, the risk of lung cancer also drops to the same risk as non-smokers.