ObjectivesTo understand stakeholders’ views regarding the content and design of paediatric clinical trial multimedia websites. To describe how this knowledge informed the development of the multimedia websites.DesignQualitative study comprising two rounds of interviews or focus groups, with thematic analysis of interview transcripts.ParticipantsSixty-two people (21 children and young people with long-term health conditions, 24 parents and 17 professionals).SettingOne UK children’s hospital and one UK Young Persons’ Advisory Group.ResultsWhen asked what was important in deciding whether to join a trial, children, young people and parents prioritised information about what participation would involve, what the trial was testing, potential benefits and risks of participation and knowing they could leave the trial if they later changed their minds. Young people and parents trusted trial teams to follow regulatory and quality requirements and therefore did not think such information was a priority for the websites, although logos of trusted organisations could lend credibility. Professionals largely concurred with these views. Children and young people advised on the importance of designing the multimedia website to ensure its appearance, tone and wording suited the intended audience and on using animated characters to facilitate children’s engagement.ConclusionsOur study provides insights into the information that families value when deciding about healthcare trial participation. It provides guidance on the design of information resources to appeal to children and young people, while also being acceptable to parents and professionals who are often gatekeepers of children’s access to information. Our findings will be of use to others developing similar multimedia websites. We report specific information needs and new visual preferences that are not usually addressed in printed trial information. Our work illustrates what qualitative research and participatory design practices can contribute to the development of information resources more generally.Trial registration numberISRCTN73136092; Pre-results.