Objectives: In the Go/NoGo task, the N2 and P3 components are often thought to index response inhibition, or conflict between competing responses. If so, they should be affected by response preparation when the prediction of an informative cue is incorrect. Methods: Twenty-six adult participants completed a cued-Go/NoGo task. Targets required a left or right button press, or no response, while cues predicted the probable identity of the target. Analyses examined (a) effects of cues on response preparation, and ‘‘inhibitory’’ components to NoGo targets, (b) typical Go/NoGo differences, and (c) the impact of cue (in)validity. Results: A reaction time benefit was associated with valid cueing, and a cost with invalid cueing. Late CNV results indicated that participants used cue information to prepare responses, and the P3, but not the N2, showed an increase with prior preparation. Typical frontal N2 and P3 NoGo > Go effects were observed, and the P3 but not the N2 showed an Invalid > Valid effect. Conclusions: The P3, rather than the N2, reflects the inhibition of a planned response and/or the conflict between competing responses. Significance: The findings suggest the need for a major review of current interpretations of the N2 and P3 in inhibitory tasks.