Converging evidence suggests that compromised motor abilities in hemiparetic cerebral palsy are not solely due to impairments in motor execution, but are also related to deficits in action planning. The present study had two aims. First, we compared grip planning in a sequential task between participants with left-sided (n = 12) or right-sided (n = 10) congenital hemiparesis. Second, we studied the use of visual information for grip planning by having participants grasp a rod embedded in a 'rod-and-frame' illusion. The results showed that especially participants with right hemiparesis revealed planning problems as most of them did not switch between different grip types at all or they switched in an inconsistent manner. In contrast, the majority of participants with left hemiparesis showed consistent planning of the first part of the task. Second, the results indicated that visual information provided by the illusion had an effect on grip planning in participants that used a consistent planning strategy, suggesting that the use of visual information in action planning was not affected in these participants. The results are discussed in relation to hemispheric differences in motor planning and visuo-motor integration in congenital hemiparesis. © 2009 Elsevier B.V. All rights reserved.