The medial prefrontal cortex (MPFC) reliably activates in social cognition and reward tasks. This study locates distinct areas for each. Participants made evaluative (positive/negative) or social (person/not a person) judgments of pictured positive or negative people and objects in a slow event-related design. Activity in an anterior rostral region (arMPFC) was significantly greater for positive than for negative persons but did not show a valence effect for objects, and this was true regardless of the judgment task. This suggests that the arMPFC is tuned to social valence. Interestingly, however, no regions of the MPFC were found to be responsive to social information independently of valence. A region-of-interest analysis of the para-anterior cingulate cortex (pACC), previously implicated in reward processing, demonstrated sensitivity to the valence of all stimuli, whether persons or objects, across tasks. Affective evaluation may be a general function of the MPFC, with some regions being tuned to more specific domains of information (e.g., social) than are others.