Several researchers have pursued the question of whether affective or cognitive persuasion appeals are more successful in changing attitudes. The vast majority of studies in this field have found that the persuasiveness of affective and cognitive appeals depends on the extent to which recipients’ existing attitudes are based on affect or cognition: Affective messages are more successful in changing affect-based attitudes; cognitive messages are more successful in changing cognition-based attitudes. However, research to date has not uncovered the processes leading to these effects. In the present article it is argued that there are two plausible explanations. First, matching messages to informational attitude bases might heighten message scrutiny. This would mean that a central process underlies the effects. Second, a peripheral process might account for the effects. Specifically, processing fluency might act as a peripheral cue. The results of an experimental study clearly suggest that that processing fluency underlies the effects.