Background: The right of children to have their voice heard has been accepted by researchers, and there are increasing numbers of qualitative health studies involving children. The ethical and methodological issues of including children in research have caused worldwide concerns, and many researchers have published articles sharing their own experiences. Objectives: To systematically review and synthesise experts’ opinions and experiences about ethical and methodological issues of including children in research, as well as related solution strategies. Research design: The research design (...) was a systematic review of opinion-based evidence, based on the guidelines by Joanna Briggs Institute. Methods: A search of five computerised databases has been conducted in April 2014 and 2271 articles were found. After screening the titles, abstracts, full texts and appraising the quality, 30 articles were finally included in the review. A meta-aggregative approach was applied in the data analysis and synthesis process. Ethical considerations: Ethical approval is not needed as it is a systematic review of published literature. Results: Six themes were identified, including evaluating potential risks and benefits, gaining access, obtaining informed consent/assent, protecting confidentiality and privacy, building rapport and collecting rich data. The similarities and differences between research involving children and that involving adults were indicated. Conclusion: All potential incentives should be justified when designing the study. Further studies need to research how to evaluate individual capacity of children and how to balance protecting children’s right to participate and their interests in the research. Cultural differences related to researching children in different regions should also be studied. (shrink)