OBJECTIVE: To investigate the change of respiratory function and relationship between pulmonary function and functional improvement following rehabilitation in acute hemiplegic stroke patients. METHOD: Thirteen stroke patients were enrolled in this study. To evaluate hemi-diaphragmatic paralysis, we checked chest radiographs in the inspiration and expiration position of all patients. When diaphragmatic paralysis was suspected, fluoroscopy of diaphragm was conducted. To evaluate respiratory function, pulmonary function test and peak cough flow (PCF) were performed before and 3 weeks after conventional rehabilitation period. To evaluate correlation of functional performance, motor and pulmonary function, Motricity index and modified Barthel index were checked also before and 3 weeks after the period. RESULTS: Only one of 13 acute stroke patients was diagnosed as diaphragmatic paralysis. At initial evaluation of pulmonary function test, restrictive pattern was observed in 5 of 13 patients and female and patients with restrictive pattern generally showed lower pulmonary function scores. After rehabilitation, forced inspiratory vital capacity (FIVC), peak expiratory flow rate (PEF), maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP) and PCF were significantly improved. Improvements of forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1), MIP and FIVC were correlated with those of MBI. CONCLUSION: Decline in respiratory function could be occurred in acute hemiplegic stroke patients. Also, respiratory function could be improved with conventional rehabilitation and may be correlated with functional improvement. Therefore, the evaluation of respiratory function and active rehabilitation therapy should be conducted in acute stage to prevent pulmonary complications and promote functional recovery.