Can minors decide what is in their interest, or do parents know better? While Art.1 of the UN Convention on the Rights of the Child defines children as “every human being below the age of 18 years”, most children are in a position to make decisions about their health earlier. In medical law cases, this can lead to difficult assessments of decision-making abilities. The “best interest” of the child (Art. 3 CRC) is usually what all parties involved strive for. However, the definition of “best interest” can be contentious, so that the courts have to balance all conflicting interests. This article aims to analyse the influence of the different parties involved in competing rights claims concerning children’s health. The following ‘best interest’ test will be used as a framework: D = ax + by + cz (D: judge’s decision, x: child’s preference, y: parents’ wishes and z: State’s interest).