Background: Although gender differences in psychopathology among the general psychiatric population appear to be well documented, such differences have been either ignored or inconsistently investigated among people with intellectual disability (ID). Methods: The study examined psychiatric co-morbidity in 295 men and 295 women with ID and significant social impairments living in community settings. The sample was drawn from consecutive clinical referrals to a specialist mental heath service of South-East London. Psychiatric diagnoses were based on ICD-10 criteria. Results: Personality disorder was more common among men, although dementia and adjustment reaction were more common among women. There were also gender differences in marital status, with a larger percentage of women being either married or in a stable relationship. Gender differences in the source of referral were also observed, with more women being referred through primary care and more men being referred through generic mental health services. Conclusions: Female patients seem to have at some extent different mental health needs from male patients. Such differences should be taken into account in the design and delivery of clinical service for people with ID.