Unlike adults, children are not granted the assumption of having decision-making capacity because their cognitive capacities are not yet fully developed. Still, child participation is increasingly encouraged within the clinical and research context. The trend towards inclusion has been initiated by the United Nations Convention on the Rights of Children (1989). The openness of the convention, however, might lead to contradictory interpretations. The notion of evolving capacities recalls mainstream developmental psychological theories that view the child as an impaired being and may hamper children's right to participation. This shows that policy measures are not a panacea and that other tools are needed to promote children's involvement in medical practice. For this purpose, the authors of this essay aim to "undo" the traditional, cognitive approach to decision-making capacity and to incorporate the conceptual framework of the capability approach in pediatrics. The capability approach encourages parents and health-care professionals to reflect on how they can foster children's role in decision-making by taking into consideration the socio-familial, cultural, and environmental context in which they live. By acknowledging that children's preferences can differ, the capability approach promotes a patient-centered approach.