Although it is generally accepted that foster children are at greater risk for mental health problems than are children in the general population, very little is known about the smaller group of foster children admitted to psychiatric hospitals. The present study sought to determine whether foster children admitted to inpatient care are a distinct and more vulnerable group than other hospitalized children and found that they are. Youth admitted from the foster care system were found to have higher rates of externalizing problems and diagnoses and lower social competence relative to other inpatient children. They were also found to have a distinguishing pattern of service use including first admissions at younger ages, higher numbers of restraints in hospital, and greater likelihood of readmission. These findings point to pressing needs for additional research to improve understanding of the vulnerabilities and inpatient care needs of foster children and for better initiatives to prevent early and recurrent hospitalization. (Contains 2 tables.)