This article assesses the impact of rural–urban migration on gender disparities in children's access to healthcare in China and India. Much research has shown widespread discrimination against girl children in both countries, including in health investments, contributing to the well-known problem of Asia's ‘missing’ women. Much less clear is the impact of the massive rural–urban migration now occurring in China and India on discrimination against daughters. Migration is usually thought to have a positive effect on child health, because of improved access to healthcare facilities, but this is not necessarily equally beneficial for both sons and daughters. Based on fourteen months of fieldwork with rural migrant families in Shenzhen (China) and Mumbai (India), this article argues that where migration improves access to healthcare, it may increase rather than decrease the gender gap in treatment of child illness in the short term, as resources are concentrated on the treatment of sons. Furthermore, it is not the case that rural–urban migration necessarily leads to better access to healthcare even for sons: some forms of migration may actually have an overall negative effect on child health outcomes. For these two reasons, development strategies focusing on large-scale rural–urban migration should not be seen as a short-term solution to problems of gender inequity in child health.