What happens to the tar in the lungs when you quit smoking?

Largely lost: Some tar is tattooed onto the lungs and fades very slowly, as do skin tattoos. It's basically harmless in this form. Unlike what you've been told, most of the tar is coughed up in the few days after you inhale it, and you swallow it. The really deadly things in smoke are the small molecules that bring in lung-damaging cells and mutate genes to precancer.