In everyday life one may encounter both unpredictable and self-initiated, hence anticipated, events. Here, we analyzed the effects of self-initiated auditory stimulus presentation on P3 and N2 components in an oddball paradigm. If the stimulus sequence was fully self-determined, both components were attenuated in comparison with computer-controlled representation. In contrast, both components were increased when only the stimulus onset was self-initiated, yet the forthcoming stimulus type was unknown. We hypothesize that predictive forward models offer an unifying explanation for the modulation of both P3 and N2 through: (a) attenuation of neuronal responses to anticipated stimuli contingent on one's own motor action and (b) enhancement of responses in case of incongruity between an anticipated action effect and the actual perceptual consequences.