The purpose of this study was to evaluate respiratory functions in relation to the gross motor functions(total value of GMFM), the difference of chest girth, and the changing position in spastic children. The respiratory functions(FVC, FEV1, $FEV1\%$, and PEF) were measured in the supine, the $45^{circ}$semi-sitting, and the $45^{circ}$sitting in 9 subjects. In the supine position, the mean difference of chest girth was $1.56{pm}0.80cm$, the total value of GMFM was $45.41{pm}17.79\%$. In the supine position, there was significant positive relationship in FVC-FEV1, FVC-PEF, and FEV1-PEF, but there was no significant relationship in GMFM and all respiratory functions. In the $45^{circ}$semi-sitting, there was significant positive relationship in GMFM-FVC, FVC-FEV1, FVC-PEF, FEV1-PEF, and $FEV1\%-PEF$. In the $90^{circ}$sitting, there was significant positive relationship in GMFM-FEV1, $GMFM-FEV1\%$, FVC-FEV1, FVC-PEF, and FEV1-PEF. In results of measured respiratory functions according to the postures, the supine position had highest value in all respiratory functions, but there were no significant (p<0.05).