Purpose: Participatory design (PD) is a collective creative design process involving designers and nondesigners. There is limited reporting on the experience of using PD for adolescent and young adult (AYA) care. This study summarizes lessons from employing PD to develop care for AYAs with cancer. Methods: A qualitative multiple-case study method was conducted of three PD processes addressing food (FfC), intimacy and sexuality (I&S), and integrative medicine (IM) in caring for AYAs with cancer. Results: Local key stakeholders, who were exposed to a problem and had not been successful at solving it individually, were recruited to ‘‘dream’’ together. Through this synergy, a shared understanding of the problem and a joint mission emerged to find a solution. PD tools were used to develop a problem definition. An open mind and explorative research helped to understand the problems, and stakeholders were managed such that idea-sharing and learning were enabled. Designers translated ideas into prototypes. The PD process was prolonged due to the hierarchical hospital environment, business considerations, and additionally required evidence. The FfC program produced an effective new food service for the whole hospital. The I&S initiative developed a podcast, two articles, and a prototype website. The IM project developed a pilot study. Conclusions: For a PD process to successfully develop care for AYAs, one needs to use designers and skilled people, PD tools, and an open-ended approach to visualize and materialize new forms of care. Furthermore, recruitment and facilitation techniques help leverage knowledge and create a synergy in a democratic environment between stakeholders.@en