Background: Chinese female adolescents engaged in sex trade and substance use are often criminalized and stigmatized. As a result of these cultural, legal and political constraints, ethical concerns can discourage investigators from engaging these adolescents in research. This paper aims to address the ethical tensions between protection and inclusion in conducting sexual and reproductive health (SRH) research with adolescents engaged in high-risk behaviours. Processes of moral reasoning, and examples and practical mechanisms in managing such ethical challenges were presented in the hope of advancing the research ethics policies and practice with adolescents. Methods: We extracted ethical issues from three previously conducted SRH studies i...