This paper describes the methodological approaches and challenges associated with tracing and contacting former social welfare service users in the course of long-term outcome research. Historical case file data were analysed on 117 ‘hard to reach’ children and young people identified as having behavioural problems, including sexual behavioural problems. Various publicly available internet and social network resources were used to try and trace these individuals in adulthood, at least a decade after the identification of their behaviour problems in childhood. Using these approaches, it was possible to locate individuals in 69 per cent of cases. The use of social network sites, such as Facebook, in social research is discussed, together with an appraisal of the practicalities and ethics of such approaches. The implications for social work practice more generally of the emergence of new technologies for tracing and maintaining contact with service users are also discussed.