In this study, we used a spirometer to measure pulmonary function of 48 patients (4.3 to 34 years old), with type II and type III spinal muscular atrophy (SMA) and compared our findings according to the two SMA types, sex, functional grade, and degree of scoliosis. SMA patients were stratified into three groups based on severity and the age at which the symptoms began: type I, type II, and type III SMA patients were also classified into four functional grades depending upon whether they were able to 1) sit with support, 2) sit independently, 3) walk with assistance, or 4) walk independently. A restrictive pattern was found in all SMA patients who were found to have impaired lung function. The highest functional group had normal or nearly normal pulmonary functions. The lowest functional group, however, were found to have the worst pulmonary functions. Patients with type III SMA had better lung function than type II. We found a significant inverse relationship between pulmonary function and scoliosis, but no significant difference in pulmonary functioning with respect to gender. As the functional grade decreases, chest care needs to be intensified to prevent respiratory tract infections.