Cognitive behavioural therapy is increasingly promoted as a treatment for chronic fatigue syndrome. There is limited research on informed consent using cognitive behavioural therapy in chronic fatigue syndrome. We undertook a narrative review to explore efficacy and to identify the salient information that should be disclosed to patients. We found a complex theoretical model underlying the rationale for psychotherapy in chronic fatigue syndrome. Cognitive behavioural therapy may bring about changes in self-reported fatigue for some patients in the short term, however there is a lack of evidence for long-term benefit or for improving physical function and cognitive behavioural therapy may cause distress if inappropriately prescribed. Therapist effects and placebo effects are important outcome factors.