Individuals with hemiplegia have difficulty planning movements, which may stem from deficits in motor imagery ability. We explored motor imagery ability in three groups of 21 children, aged 8–12 years: children with hemiplegia; children with developmental coordination disorder (DCD); and a comparison group. They completed two tasks requiring laterality judgments of body parts—hand and whole-body rotation. Accuracy in both was reduced for the motor-impaired groups, and response time was atypical for the whole-body task. This suggests that motor imagery deficits exist in children with hemiplegia and DCD, supporting previous findings that planning deficits in hemiplegia may result from deficits in motor imagery.