Section 3(2) of the Mental Capacity Act 2005 requires doctors to take practical steps to help a person with impaired capacity to make a competent medical decision. This legal duty does not extend to minors under the age of 16. They must prove their competence where it is presumed in adults, and they can only make decisions in their best interests. Yet the General Medical Council's End of Life Treatment and Care guidance (2010) requires doctors to maximise a patient's capacity, and does not restrict its application to adults. This paper explores the implications of such a duty insofar as it applies to minors. If there is a duty to maximise a child's capacity to consent then the same duty applies when a child withholds consent. A child's competent decision to refuse treatment can be overruled in his best interests, but arguably the development of human rights increases the significance of capacity when determining best interests. If this is the limit of a competent child's right to give or refuse consent, then it is important to ensure that the child has an adequate opportunity to demonstrate his capacity. In this paper I argue that there is much to gain from maximising a child's capacity to consent, but there are also dangers that paternalism will creep in through the back door.