Objectives: Anxiety is more prevalent in children with chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) than in the general population. A systematic review was carried out to identify which treatment methods are most effective for children with CFS and anxiety. Design: Systematic review using search terms entered into the Cochrane library and Ovid to search the databases Medline, Embase and psychINFO. Participants: Studies were selected if participants were <18 years old, diagnosed with CFS/ME (using US Centers for Disease Control and Prevention, the National Institute for Health and Care Excellence or Oxford criteria) and had a valid assessment of anxiety. Interventions: We included observational studies and randomised controlled trials. Comparison: Any or none. Outcomes: Change in anxiety diagnostic status and/or change in anxiety severity on a validated measure of anxiety from pretreatment to post-treatment. Results: The review identified nine papers from eight studies that met the inclusion criteria. None of the studies specifically targeted anxiety but six studies tested an intervention and measured anxiety as a secondary outcome. Of these studies, four used a cognitive behavioural therapy (CBT)-type approach to treat CFS/ME, one used a behavioural approach and one compared a drug treatment, gammaglobulin with a placebo. Three of the CBT-type studies described an improvement in anxiety as did the trial of gammaglobulin. As none of the studies stratified outcomes according to anxiety diagnostic status or severity, we were unable to determine whether anxiety changed prognosis or whether treatments were equally effective in those with comorbid anxiety compared with those without. Conclusion: We do not know what treatment should be offered for children with both anxiety and CFS/ME. Further research is therefore required to answer this question.