Like many of us here I gave up the cigarettes in order to get more fit. This was in January 2000. I didn't noticeably suffer from shortness of breath althou I did occasionally get bronchitis which lasted a while. After a couple of months from giving up - the breathlessness started - not bad at first but I could no longer jog - I felt better after a puff of ventolin. At this time I really got into the exercising regime, but like others the breathlessness got progressively worse.
No medico nor report has really given me an explanation for the delayed reaction after giving fags away.