Inhibition of prepotent responses plays a key role in cognitive executive control of goal-directed behavior. Response inhibition in Go/No-Go tasks elicits a distinct midfrontal ERP component, the N2, localized in previous studies to the anterior cingulate cortex. We assessed heritability of the No-Go N2 and the succeeding positive P3 component in 194 young female twins (52 monozygotic and 45 dizygotic pairs) who completed a cued version of the Continuous Performance Test. Genetic model-fitting analysis showed that about 60% of the variance in N2 and P3 amplitudes can be attributed to genetic factors, suggesting that frontal No-Go N2 and P3 components may index genetically transmitted individual differences in brain activity related to conflict processing and can potentially serve as endophenotypes for genetic studies of disorders characterized by neurobehavioral disinhibition.