The aim of this study is to examine what social workers consider as ‘challenging behaviour’ among adolescents, but also to examine the connection between investigation and intervention in cases where such behaviour is being displayed. The questions of the study are to examine what social workers think of the instrument of assessment BBIC (Children’s Needs in Focus) and how the usage of BBIC affect social workers understanding of challenging behaviour. Moreover, it is a qualitative study and the respondents are all social workers with various length of professional experience who work with making decisions in juvenile welfare cases. The social workers’ opinion about which behaviours among adolescents that were important to intervene in could be understood with what was considered as moral panic for some behaviour. The social workers use of and opinion towards BBIC could be understood in relation to practical theory, tacit knowledge and naïve theories.