In a previous study we developed a cognitive assessment battery called the Pediatric Powered Wheelchair Screening Test (PPWST) to help clinicians determine a young child's readiness to drive a powered wheelchair. The current multicenter study sought to determine: (1) whether the PPWST is appropriate for use in a population of children with cerebral palsy (CP) who use joysticks to drive their wheelchair; (2) whether two additional factors (symbolic representation and coping) would increase the predictive power of the PPWST for this group and for children with orthopedic or neuromuscular disabilities only; and (3) whether the test was appropriate for children with severe motor impairments who use switches to control their wheelchair. Fifty children (27 males, 23 females) between the ages of 21 months and 6 years 11 months participated. Twenty-six children (mean age 4 years 4 months, SD 15 months) had triplegic or tetraplegic CP and 24 children (mean age 27 months, SD 5 months) had orthopedic or neuromuscular disabilities. Sixty-nine per cent of children had some limited form of mobility (such as rolling or scooting) but none was a functional ambulator. Each child was assessed with the PPWST and with measures of symbolic representation and coping. After six wheelchair training sessions, driving ability was scored. The PPWST was found to be predictive of functional driving ability for children with CP who used a joystick to control their wheelchair. Assessment of symbolic representation skills increased the predictive power for this group but not for children with orthopedic or neuromuscular disabilities; coping scores did not increase the predictive power for either group. The PPWST accounted for only 20% of the variance in overall driving skills for switch users, and thus is not yet considered an adequate screening device for this group. The PPWST is designed to help clinicians determine whether a child currently has the specific cognitive skills found to be related to powered wheelchair driving but is not intended to be used exclusively to determine whether or not a child is ultimately a candidate for powered mobility.