This study investigated the effects of seat cushion material during a reaching task. Ten healthy adults and three individuals with cerebral palsy participated. All subjects performed the reaching task on two urethane cushions and one silicone cushion. Anterior/posterior and medial/lateral displacement of the center of pressure and straight rate were assessed. In addition, the movement trajectory of the hand was recorded. No differences among seat cushions were observed in healthy adults. However, all of individuals with cerebral palsy were able to perform the task more efficiency while seated on the silicone cushion than the others. These findings suggest that seat cushion design may improve movement in individuals with cerebral palsy who have postural control disabilities.