Adequate participation of children and adolescents in their healthcare is a value underlined by several professional associations. However, little guidance exists as to how this principle can be successfully translated into practice. A total of 52 semi-structured interviews were carried out with 19 parents, 17 children, and 16 pediatric oncologists. Questions pertained to participants' experiences with patient participation in communication and decision-making. Applied thematic analysis was used to identify themes with regard to participation. Three main themes were identified: (a) modes of participation that captured the different ways in which children and adolescents were involved in their healthcare; (b) regulating participation, that is, regulatory mechanisms that allowed children, parents, and oncologists to adapt patient involvement in communication and decision-making; and (c) other factors that influenced patient participation. This last theme included aspects that had an overall impact on how children participated. Patient participation in pediatrics is a complex issue and physicians face considerable challenges in facilitating adequate involvement of children and adolescents in this setting. Nonetheless, they occupy a central role in creating room for choice and guiding parents in involving their child.