Résumé : Despite group-based patient and public involvement (PPI) initiatives in oncology research being a growing trend, little research has been conducted on the added value of PPI according to the personal experiences of its contributors. This study aims to describe the personal experiences of PPI group members and coordinators in Flanders (Belgium) to investigate the dimensions of individual and collective added value of group-based PPI initiatives as well as the challenges in realizing this added value.