If you smoke and at the same time got asthma this can in the long run cause that the airways get chronic thight and narrow and the asthma evolves into Chronic obstructive pulmonary disease (COPD), also known as Chronic obstructive lung disease (COLD), in Norway known as KOLS, and in Sweden KOL. To avoid this the smoker having asthma should stop smoking and just hope that it is not to late. It is the only way.
Besides that this shows the consequence of smoking:
On the left you see a healty lung from a non-smoker, and on the right you see a lung from a smoker that has smoked one pack of cigarettes a day for twenty years. Scary if you ask me.