Psychobiological accounts of face processing predict that greater salience is attributed to faces matching a viewer's sexual preference than to faces that do not. However, behaviorally, this effect could only be demonstrated in tasks assessing reward 'wanting' (e.g. work-per-view-tasks) but not in tasks assessing 'liking' (e.g. facial attractiveness ratings), and has been found to be more pronounced in heterosexual men than women, especially with regard to very attractive faces. Here, we addressed the question if sex differences at the level of 'wanting' persist if participants are uninformed about the attractiveness of an anticipated male or female face. Seventeen heterosexual men and 13 heterosexual women (all single) participated in a social incentive delay task (SID). Participants were required to react on simple graphical cues in order to view a smiling face. Cues provided a priori information on the level of smile intensity (low/medium/high) as well as sex of the face (male/ female). A significant interaction of sex-of-face and sex-of-participant was observed in a priori defined regions of interest in the brain reward system (including ventral tegmental area, nucleus accumbens and ventromedial prefrontal cortex), reflecting enhanced activation to cues signaling opposite-sex faces relative to same-sex faces in both, men and women. Women additionally recruited the temporo-parietal junction (TPJ) during processing of opposite- vs. same-sex cues, suggesting stronger incorporation of social cognition processes in women than men. The findings speak against a general male bias for opposite-sex faces. Instead they provide preliminary evidence that men and women recruit different brain circuits during reward value assessment of facial stimuli.