BACKGROUND:　Smoking　for　a　long　period　is　known　to　cause　several　harms　to　the　human　body,　chiefly　associated　with　serious　pulmonary　damage.　OBJECTIVE:　The　purpose　of　this　study　was　to　evaluate　the　difference　in　the　pulmonary　damage　between　current　smokers　and　ex-smokers,　through　measuring　the　bronchial　parameters　and　the　extent　of　emphysema,　in　order　to　further　illustrate　the　harm　of　smoking　and　the　need　to　stop　smoking.　METHODS:　Using　the　FACT-Digital　lung　TM　software　quantitatively　analysis　of　CT　images,　including　the　WT,　WA%,　LD,　LV,　PD,　and　%LAA-950　was　performed.　The　percentage　of　low　attenuation　areas　less　than　-950　Hounsfield　units　(%LAA-950)　was　defined　as　the　extent　of　emphysema.　The　longitudinal　data　in　the　two　consecutive　years　of　these　current　smoker　group　and　ex-smoker　group　were　compared　by　paired　t-test.　RESULTS:　The　LV,　%LAA-950,　WT　and　WA%　of　current　smokers　increased　more　rapidly　each　year　than　that　of　ex-smokers.　The　PD　and　LD　of　current　smokers　declined　more　rapidly　each　year　than　that　of　ex-smokers.　CONCLUSIONS:　This　study　shows　that　pulmonary　damage　caused　by　smoking　related　to　the　smoking　status,　can　be　measured.　Smoking　cessation　has　a　positive　role　in　alleviating　the　progress　of　pulmonary　damage.