Tobacco smoking is widely prevalent all over the world and it continues to rise in developing countries. Smoking has a deleterious effect on pulmonary functions. Smoking is the single most significant risk factor contributing to the development of Chronic obstructive airway diseases (COPD). Spirometry by a trained health professional gives an indication of lung health by measuring airway abnormality. Objectives were to study pulmonary function test (PFT) in asymptomatic smokers. The study was carried out in JSS Hospital, Mysore over the period of two years . The study was designed as cross section study which included 449 subjects of which 224 were in group 1 ( 0-10 Pack Year), 139 were in group2 (11-20 Pack Years), and 87 were in group 3 ( 21- 30 Pack Years ). Subjects with history of cigarette smoking and no respiratory symptoms were subjected spirometry. Forced Vital Capacity (FVC), Timed Vital Capacity(TVC) FEV1 was included in this study . The mean value of FVC-POST in group 1 (0-10pack years) is 3.323+0.696 , in group 2 (11-20pack years) is 2.992+0.679 , and in group 3 (21-30 pack years ) is 2.741+0.632 respectively. The mean values of FEV1-POST in group 1(0-10 pack years) is 2.76+0.631, Group 2 (11-20 pack years) is 2.359+0.623 and Group 3 (21-30pack years) is 1.920+0.513 respectively. The mean value of FEV1/FVC POST in Group 1(0-10pack years) is 0.831+0.575, In Group 2 (11- 20pack years) is 0.784+0.075, and in Group 3 (21-30pack years) is 0.696+0.079 respectively. From the present, by comparing the Pulmonary Function Test parameters in group1 (0- 10 pack years), group2 (11-20 pack years), and group 3 (21- 30 pack years), we conclude that cigarette smoking was found to cause decrease in various Pulmonary Function Test parameters and leads to airway obstruction.