This paper examines the impacts of rural-urban migration on migrant children’s health in China, in particular focusing on gender disparities in access to healthcare. Much research has shown discrimination against girl children, including in health investments, contributing to the well-known problem of Asia’s ‘missing’ women. Much less clear, though, is the impact of China’s massive rural-urban migration of the last 20 years. Migration is usually thought to have a positive effect on child health, because of improved access to healthcare facilities. However, this is not always the case, and even where access improves it is not necessarily equally beneficial for both sons and daughters. Drawing on fieldwork with rural migrant families in Shenzhen, this paper argues that migration may increase rather than decrease gender gaps in treatment of child illness in the short term, and that this may be exacerbated by China’s hukou (household registration) policy. The second part of the paper explores the likely impacts of the historic 2014 hukou reform proposals, which reportedly aim to improve equity of access to healthcare and other welfare services. It argues that the reforms may in fact have the opposite effect, introducing new inequalities, and entrenching existing ones further.