Background: Intolerance of uncertainty (IU), negative beliefs about worry (NBW), positive beliefs about worry (PBW), negative problem orientation (NPO) and cognitive avoidance (CA) have been found to be integral in the conceptualisation of Generalised Anxiety Disorder (GAD) in adults, yet they have rarely been investigated in children with GAD. This study sought to determine (a) whether IU, NBW, PBW, NPO and CA differ between children diagnosed with GAD and non-anxious children and (b) to examine whether IU, NBW, PBW, NPO and CA differ between parents of children diagnosed with GAD and parents of children without an anxiety disorder. Methods: Participants were 50 children (aged 7–12 years), plus one of their parents. The 25 GAD children and 25 non-anxious children were matched on age and gender. Parents and children completed clinical diagnostic interviews, as well as a battery of questionnaires measuring worry, IU, NBW, PBW, NPO and CA. Results: Children with GAD endorsed significantly higher levels of worry, IU, NBW, NPO and CA, but not PBW compared to non-anxious children. Parents of children with GAD did not differ from parents of nonanxious children on any of the variables. Limitations: The study was limited by it's use of modified adult measures for some variables and a lack of heterogeneity in the sample. Conclusions: The cognitive variables of IU, NBW, NPO and CA may also be important in the conceptualisation and treatment of GAD in children as they are in adults