We used event-related potentials (ERPs) to investigate the mental processes that contribute to affective priming (AP), a systematic shift of evaluative judgments about neutral targets toward the valence of preceding primes. 64 participants rated their liking of a priori neutral ideographs preceded by 800-ms emotional primewords, while 64-channel EEG was recorded. We observed a significant AP effect that was closely associated with prime valence dependent variations of the right central-to-parieto-occipital positive slow wave (PSW) amplitude in the target ERP, providing evidence for implicit affect misattribution as one source of the effect. While deeper target processing mirrored in valence unspecific central-to-parieto-occipital target PSW amplitude was negatively associated with AP, deeper prime processing indicated by valence unspecific central-to-parieto-occipital prime PSW amplitude was positively related to AP. These depth of processing effects underline the importance of strategic processes in AP. In a stepwise linear regression analysis, the prime valence effect on right central-to-parieto-occipital target PSW indicating affect misattribution and the two valence-unspecific ERP indices of processing depth (central-to-parieto-occipital prime- and target PSW) were independent predictors of the size of the AP effect. Together they accounted for 60% of the variance. Furthermore, an explorative analysis provided first evidence for the relevance of early discrimination of prime valence for AP.