When mature minors face a decision with important consequences, such as whether to undergo a risky but potentially life-saving medical procedure, who should decide? Relying on liberal political theory’s account of the importance of decisional autonomy for adults, and given the scalar nature of the capacities needed to exercise decisional autonomy, I argue that mature minors with the requisite capacities and commitments have a right to decisional autonomy though they are not yet 18. I argue for this right using a (...) ‘balancing of interest’ account of rights: the interest mature minors have in decisional autonomy outweighs their parents’ interest in shaping their children as a means of ‘creative self-extension’. But I propose two limitations on this right: requests for waivers of the rule that one must be at least 18 to decide cannot be so numerous as to make adjudication impractical; and though a competent adult’s voluntary decision to refuse medical treatment should generally be respected, the state may reject a mature minor’s decision upon review by an indifferent judge of the minor’s capacities and reasons. The judge reviews not the substantive merits or prudence of the decision, but whether the decision promotes the interest in decisional autonomy, by asking among other things whether the decision is the minor’s own, is tethered to core commitments rather than based on arbitrary preferences, and could be regarded as reasonable to the minor’s ‘future self’. (shrink)