Given the lack of knowledge about safety and efficacy of many treatments for children, pediatric clinical trials are important, but recruitment for pediatric research is difficult. Little is known about children's perspective on participating in trials. The purpose of this study was to understand the experiences and motivations of young people who took part in clinical trials. This is a qualitative interview study of 25 young people aged 10-23 who were invited to take part in clinical trials. Interviews were audio or video recorded and analyzed using framework analysis. Young peoples' motivations were both personal benefit and helping others. Both incentives appeared to be more complex than expected. We introduce the terms "network of exchange" and "intergenerational solidarity" to describe these motivations. To improve recruitment, professionals should be more open about research opportunities, provide better information, and give young people feedback after the trial has ended.