This paper briefly reviews existing evidence concerning psychosocial interventions for adults with intellectual disabilities and mental health problems. Research evidence concerning the epidemiology of mental health problems in adults with intellectual disabilities is discussed, focusing on issues in the reliable and valid identification of mental health problems in this user group and the results of prevalence studies. Current evidence concerning the use and effectiveness of psychosocial interventions for people with intellectual disabilities and mental health problems is then outlined. Particular attention is paid to cognitive-behavioural interventions. Finally, issues concerned with adapting psychosocial interventions for people with intellectual disabilities and mental health problems are discussed, focusing on issues of informed consent and assessment of suitability for CBT.