This study is conducted to assess the the effect of chronic cigarette smoking on FEV1,FEF25-75 and their role in early detecting of COPD. Subjects aged 40 years or older and who smoke 10 packs per year or more (n=110) were selected, the smoking histories of these subjects were investigated using a self-reported questionnaire, there were 5 smokers with restrictive disease, these patients were removed because they should be referred for further lung function, Percent predicted values of measured spirometric parameters of( FEV1, FEF25-75 ) decreased significantly with increasing pack-years (p-value <0.05 for male and female ) and there was an increasing in chronic respiratory symptoms frequency, so these Indices decrease must be considered as high risk to develop COPD. According to the interpretation of spirometric results %63 smokers had normal spirometry while 37% smokers had confirmed COPD using (GOLD) severity criteria, smokers having COPD (87% male and 13% female ),these patient were divided into grades I ( 6.66%), II(17.14%), III(11.42%), IV( 1.9%).