The extent to which cognitive behaviour therapy can be used with children is unclear. In meta analyses older children and teenagers seem to derive greater benefit than young children. This may be because the cognitive immaturity of young children means that they cannot manage the cognitive demands of cognitive behaviour therapy. This paper seeks to establish how well children aged 7-8 and aged 10-11 can complete a task requiring them to distinguish between thoughts and behaviours (based on Greenberger & Padesky, 1995). Half of the children were provided with a visual cue and half were not. The effects of age, the visual cue, and verbal IQ on performance were examined. Seventy-two children were randomized to the cue and no-cue condition and individually tested during school time. Both age groups performed well and there was a significant difference between older and younger children, with the older children performing better. Visual cues did not aid performance. Verbal IQ was significantly associated with performance in the younger but not the older children. The implications of these results for the delivery of cognitive behaviour therapy with children and future research are discussed.