Objective : The aims of this study was to investigate the effects of modified constraint induced movement therapy(CIMT) on upper extremities function of children with hemiplegic cerebral palsy. Methods : The participants of this study are 4 children with hemiplegic cerebral palsy aged between 8 to 11 years old. During the modified CIMT period, the unaffected hand of the subjects was restrained by a hand splint for 8 weeks, five days per week, five hours a day. And the affected upper extremity was strongly trained by performing functional tasks, which were individually structured use of the affected arm. Measurements used to assess hand function are Jebsen Hand Function Test, and 3D Motion Analysis. The Jebsen Hand Function Test was performed repeatedly every two weeks. The 3D Motion Analysis was performed before and after the 8 weeks of modified constraint induced movement therapy. Results : After the modified CIMT, there was a significant improvement in completed time for the 6 tasks of Jebsen Hand Function Test(p<.05). 3D Motion Analysis was that the finger tapping and the hand tapping has been significantly decreased (p<.05), and the pronation-supination movement has been significantly increased as well(p<.05). Conclusion : In the results of this study, it is evidenced that modified CIMT is effective treatment for upper extremities function of children with hemiplegic cerebral palsy. For future research, it is recommended to examine various periods and protocol of modified CIMT including impact of long periods application.