Our country is facing dual burden of underweight and overweight. There is a need to address to understand the correlation between BMI(Body Mass Index) and the pulmonary functions. It seems obvious that vital capacity will be affected in underweight, overweight and obese individuals but the extent to which it may be affected is not clear. A total of 88 subjects who met the criteria were included and categorized into the underweight, normal weight, overweight and obese group on the basis of WHO BMI classification. 20, 30, 23 and 15 subjects were classified in different groups as underweight, normal weight, overweight and obese group.  Pulmonary function test of all subjects was done. The essential parameters were Tidal volume, Forceful vital capacity, forced expiratory volume in one second, FEV1/FVC% and minute voluntary ventilation. The results showed thatthere is no relation between vital capacity and BMI in young adults.The noteworthy outcome of this study was that all groups of BMI had reduced vital capacity.