Child welfare involvement is related to involvement with poverty, but the dimensions of that relationship have not been fully explored. Data from the National Survey of Child and Adolescent Well-Being were used to test the relationship between poverty indicators and placement into foster care. Poverty, ages of children, urban or nonurban settings, and the presence of mental health disorders interact to contribute to placement decisions. In urban areas, poverty is strongly associated with involvement with child welfare services, but children's mental health problems are not. In nonurban areas, children's mental health problems are a far greater contributor to child welfare involvement than poverty. Implications for understanding the dual functions of child welfare placements are provided. Child welfare services continue to address the needs of families with children with substantial behavioral problems--yet, federal child welfare policy includes no recognition of this important role.