Can a smokers lung ever be fully repaired?

Perhaps: It can take a very long time for smokers lungs to recover from injury. In fact your risk of both cardiac disease and lung cancer do not go back down to normal for 10-15 years after you stop. Smokers loose a lot more lung function per year while non smokers only loose a small amount of lung function per year.

Yes it can: Depends on how much damage. If there is severe bronchitis with scarring, or emphysema damaging the air sacs, that does not heal. But lesser levels of damage heal a great deal, and in most smokers, their lungs return fully to normal after several years. Most importantly, you are not continuing to do more damage, as well as increasing chance for cancer and heart attack. Try a support program!