Pulmonary function values are influenced by race, age, sex, height, weight, waist, hip circumference as well as environmental, genetic, socioeconomic parameter. The development of pulmonary function and growth of physical parameters are coexistent. Measurement of lung function is essential for evaluation of physical development of children and adolescents. The present work was undertaken to evaluate pulmonary function in normal healthy school children of age group 13-19 years having different body mass index. The study was conducted over 300 students (13-19 years.), 155 male subjects and 145 female subjects. Pulmonary function parameters FVC, FEV1, FEV1%, FEF25-75%, PEFR, MVV, were measured by medspiror. BMI was calculated of all subjects by measuring height and weight. BMI was classified into various groups. It was found that 262 subjects had low BMI and were underweight, PFT parameters were low in these subjects as compared to subjects having normal BMI. Early identification of risk individuals prior to onset of disease is imperative in our developing country. It is necessary to have a good physical activity and proper nutrition in young individuals to avoid future respiratory problems.