My friend has COPD. I am persuading him to quit smoking but he is unsure that it will really help him breathe better. Will it?

Quitting smoking is the one thing that has been proven to slow the progression of COPD. In addition to reduction in respiratory illnesses, stopping smoking also reduces the risk for heart disease, stroke, peripheral vascular disease etc. Smoking cessation also lowers the risk for lung cancer and many other types of cancer. Earlier you quit, greater are the benefits