Background Research is crucial to improve treatment, survival and quality of life for children with cancer. However, recruitment of children for research raises ethical challenges. The aim of this study was to explore and describe ethical values and challenges related to the recruitment of children with cancer for research, from the perspectives and experiences of healthcare professionals in the Swedish context. Another aim was to explore their perceptions of research ethics competence in recruiting children for research. Methods An explorative qualitative (...) study using semi-structured interviews with key informants. Seven physicians and ten nurses were interviewed. Interviews were analysed using inductive qualitative content analysis. Results The respondents’ ethical challenges and values in recruitment mainly concerned establishing relationships and trust, meeting informational needs, acknowledging vulnerability, and balancing roles and interests. Ensuring ethical competence was raised as important, and interpersonal and communicative skills were highlighted. Conclusion This study provides empirical insight into recruitment of children with cancer, from the perspectives of healthcare professionals. It also contributes to the understanding of recruitment as a relational process, where aspects of vulnerability, trust and relationship building are important, alongside meeting informational needs. The results provide knowledge on the complexities raised by paediatric research and underpin the importance of building research ethics competence to ensure that the rights and interests of children with cancer are protected in research. (shrink)