A series of decisions by superior courts exercising their parens patriae jurisdiction in Australia, New Zealand, the United Kingdom and Canada has overturned decisions by parents, and by minors, including some close to the age of 18, to decline life-saving treatment on the basis that such treatment is “in the best interests” of the children concerned. This article reviews the reasoning in such cases and analyses the justifications proffered for giving limited weight to the expressed wishes of children and even of their parents in such matters. It identifies that the issues have particularly arisen in respect of families that are Jehovah’s Witnesses and also where there is strong opposition to the application of mainstream medicine in the context of burdensome treatment for life-threatening conditions. It acknowledges the seriousness of such decisions and the potential for collateral influences that are difficult to identify to exert significant impact upon wishes expressed in respect of children who are seriously ill. It also accepts the complexities of identifying the “real wishes” of children. However, it contends that in appropriate cases flexibility in determining children’s overall best interests is necessary and that the autonomy otherwise given to mature minors should play a more significant role in courts’ decision-making in respect of the authorisation of treatment that children have purported to decline.