Not too late to stop. Cough is a very common symptom in smokers.Especially if you are a chronic smoker, the chance that you have a chronic lung disease-like emphysema, bronchitis etc-is very high. As you know, the more cigarettes and the longer you've smoked it- the higher your risk for lung cancer. Your cough could be related to your bronchitis/emphysema vs infection vs lung cancer etc. Quit smoking and see your md!