This study examined the effect of response selection and execution on P3 latency during the performance of simple reaction time (RT) and stimulus-response compatibility tasks. Response time on these tasks was defined in terms of RT and movement time (MT). Event-related brain potentials were recorded from 67 female participants concurrently with the performance measures. On the simple RT task, the distance of the response button from the home button was varied (7, 15, and 23 cm). When stimulus evaluation demands were minimal, response execution affected P3 latency, with increased response button distance resulting in increased P3 latency. However, these movement effects were modest, and in most protocols, would not be a confounding factor. The stimulus-response compatibility task examined the interaction of stimulus evaluation demands and response requirements. RT, MT, and P3 latency were affected by stimulus congruency, whereas RT and P3 amplitude were affected by response compatibility.