A recent but growing literature has explored the implications of federally-funded child care subsidies for child well-being. While subsidies have been shown to move children into child care settings of higher observed quality, and high quality care has been associated with improved school readiness, some evidence suggests that subsidy use is associated with neutral or negative child outcomes. These findings may be explained by patterns of care choice among subsidy receiving mothers. This study investigates whether household structure moderates the association between subsidy receipt and choice of child care arrangement using samples drawn from two demographically distinct data sources: the exclusively urban Fragile Families and Child Wellbeing Study (FFCWS) and the nationally representative Early Childhood Longitudinal Study- Birth Cohort (ECLS-B). Results indicate that household structure alters the association between subsidy use and care arrangement, but the moderating role of household structure differs across the two samples. In the FFCWS, living with extended family increased the likelihood that mothers use subsidies for informal family, friend, and neighbor (FFN) care rather than center based care; in the ECLS-B, living with extended family decreased the likelihood of mothers using subsidies for informal FFN care versus center-based care. Findings suggest that household structure is an important moderator of subsidy use, but that its impact may depend on contextual and demographic factors. (author abstract)