Most countries grant parents rebuttable legal rights to make treatment decisions on behalf of their young children, creating a presumption in favor of parental rights. This article identifies and provides a preliminary assessment of a perhaps surprising variety of arguments for the presumption in favor of this parental right. The arguments considered include those flowing from ideas that parents are motivated by their child's best interests; that they have privileged insight into their child's preferences and capacities; that parental support has clinical significance and may be contingent upon respect for the presumption; that parents and families typically bear the burden of treatment decisions; that parents' views often have a religious basis; that it would be improper to override parents' wishes other than in conditions of complete certainty; and that parents have 'natural authority' over their children. It is unlikely that this is an exhaustive list of the arguments that could be offered in favor of the presumption, and the treatment in the paper is brief. Nevertheless, it is hoped that enough is said to suggest that it is harder to defend the presumption than we might have supposed.