It is now well established that the prevalence of mental health difficulties in 
individuals with autism spectrum disorders (ASD) is considerably higher than in 
the general population. With recent estimates of the prevalence of autism 
spectrum disorders being as high as one percent, increasing numbers of children 
and young people are presenting to local and specialist services with mental 
health problems in addition to a diagnosis of ASD. Many families report that the 
impact of the mental health problems can be as or more impairing than the autism 
spectrum difficulties themselves. Clinical services are frequently called upon 
to treat these difficulties; however, there is limited evidence for the 
effectiveness of treatments in this population. This paper reports a case series 
of children and adolescents with ASD and an anxiety disorder who were treated 
with a standard cognitive behaviour therapy (CBT) rationale adapted to take 
account of the neuropsychological features of ASD. Common features of the 
presentation of the disorders and also treatment processes are discussed.