The relationships between research, policy and practice in improving the mental and emotional well-being of looked after children are complex. There is a growing body of research that demonstrates that children in state care (or 'looked after children') are particularly vulnerable in terms of poor health and mental health outcomes. The current health and social care policy context is in the midst of tremendous change. Within this 'modernisation agenda' the mental health of looked after children has received welcome attention, and this in turn has stimulated a major expansion in specialist mental health services for looked after children across the UK. However, despite what we know about some of the problems looked after children face, we know very little about what is effective. Although the available evidence from research now gives a stronger indication about prevalence and identifiable risk factors for morbidity (or co-morbidity), it does little to assist in identifying what interventions are effective in improving mental health with this client group. Efforts now need to be made by practitioners, policy-makers and researchers to collectively concentrate on filling some of the gaps in our knowledge. This includes making better use of the evaluations of current services to inform the development of these services.