This article presents the findings of socio-legal comparative research into the implementation of the UN Convention on the Rights of the Child 1989 (UNCRC 1989) in the care and protection of unaccompanied asylum seeking children (UASC) in England, Ireland and Sweden. This article begins by giving the background to the research and explaining the empirical methods used. The findings are reported in relation to one primary research question: what are the key barriers to implementation of the UNCRC 1989 in the care and protection of UASC in England, Ireland and Sweden. Analysis of the empirical data identifies three key barriers to implementation: indeterminacy of the best interest principle, ill-defined and implemented special protection and assistance measures, and lack of defined service objectives. The article concludes with recommendations for the further development of the implementation of the UNCRC 1989 in the care and protection of UASC in the three states and more generally.