Despite the negative impact of anxiety in children, theories and research have lagged behind their adult counterparts. This special issue arose from an Economic and Social Research Council funded seminar series (Child Anxiety Theory and Treatment, CATTS). It highlights four themes in theories and research into child anxiety: the appropriateness of applying adult models to children, the need to isolate causal variables, the need to take a developmental perspective, and the importance of parents. This issue aims to stimulate debate about theoretical issues that will inform future child anxiety research.