This paper reports on a study that examined the co-morbidity of health and mental health problems in children and youth by investigating: (1) the prevalence of significant health and mental health problems among children with either a health or mental health disability; (2) how these prevalence rates compare to a general sample of children in families receiving Temporary Assistance to Needy Families; and (3) the rate of unmet service needs among children with co-occurring mental health disabilities. Children (n=1,145) either had no disability or received Supplemental Security Income because of a health disability (n=161) or had an identified mental health disability (n=220). Child caregivers completed a questionnaire. Findings indicated that the rate at which children with an identified mental health disability were found to have an existing health problem (37.8%) was similar to the rate at which children with an identified health disability were found to have an existing mental health problem (37%). Among both groups of children, the likelihood of having current co-morbid health and mental health problems was approximately 26%. In both groups of children with disabilities, unmet mental health needs were found to be 2 to 3 times higher than were unmet health needs. Three policy recommendations supported by the study conclude the report. (Contains 19 references.) (DB)