Children with cancer experience many symptoms and problems that often remain unreported and untreated. We therefore, developed PedsChoice, a support system for pediatric cancer symptom assessment and manage ment to provide children with a 'voice,' and assist nur ses and physicians to better address children's sympto ms and problems in patient care. We used participator y design techniques where healthy children joined our design team. During this process we explored the role s healthy children can appropriately play to inform the design of a system for children with cancer and their contributions and limitations as participants in the design process. We found that healthy children can contribute considerably in the role as testers, informers and to some extent as partners. Children have very creative design ideas that can considerably improve the software. However, system development for seriously ill children also requires psychological and pedagogical insights and design and usability expertise. This limits the role children can play as full design partners.