Institutional rearing is associated with deficits in executive functions, such as inhibitory control, and may contribute to later externalizing behavior problems. In the current study, we explored the impact of institutional rearing on attention in the context of inhibiting a planned action. As part of the Bucharest Early Intervention Project (BEIP), children were randomized to either remain in the institutions in which they lived (Care as Usual Group) or be placed into foster family homes (Foster Care Group). We also recruited age and gender matched never-institutionalized (NIG) children from the Bucharest community. We examined differences in behavioral and Event Related Potentials (ERPs) during a go-no-go task when children were 12 years old. Results revealed that the ever-institutionalized group (CAUG and FCG combined) showed slower reaction times, worse performance accuracy, larger P2 activation, and smaller (less negative) N2 activation than the NIG group. Results of a moderation analysis revealed that children who spent more time in institutions and had small N2s showed more externalizing symptoms. These results have implications for the design of treatment approaches for previously institutionalized children with externalizing behavior problems.