This article addresses the autonomy of children and adolescents in healthcare decisions, focusing on those ones that might entail a risk to the child’s life or health, especially when a medical intervention is refused. In these cases, a conflict between the recognition of the autonomy of the child and his or her protection arises, and various legal systems solve it in different ways. This study examines this issue from a comparative perspective between Belgian and Spanish laws, taking into account that the latter was rewritten in 2015 to leave out all underage patients’ decisions that could constitute a risk for their life or health.