Introduction: Forced vital capacity (FVC) is the maximum volume of air that can be expired, when a subject tries as forcefully and rapidly as possible, after a maximal inspiration to total lung capacity. A maneuver performed similarly beginning at residual volume and inspiring as forcefully as possible is called forced inspiratory vital capacity. Methodology: The tests are done by selecting chronic smokers of different age group from 3070 years from out patient and impatient from the department of TB & chest diseases, medical college. Control groups are selected from patient who does not smoke. The instrument used was a portable smallcomputerized spirometer called “Compact Vitalograph”. Results: In smokers with overweight the mean is 61.14 and the standard deviation is 22.93. When this value is tested using chisquare test, it is found that there is significant difference, according to the chisquare test the P value is less than 0.05. Conclusion: The effect of smoking on FVC is more affected in overweight group of subjects than the normal weight group of subjects.

Keywords: Forced Vital Capacity; Compact Vitalograph; Overweight.