People rapidly form evaluative impressions of other people from minimal information. In the last decade, many cognitive neuroscience studies have explored the neural underpinnings of how impressions of other people, or person impressions, are made. This chapter reviews studies on the forming of impressions from facial appearance and from behavioral information. Across studies on impressions made from facial appearance, the most consistently activated brain regions include the amygdala, nucleus accumbens, medial orbitofrontal cortex, medial prefrontal cortex (PFC), and pregenual anterior cingulate cortex. Across studies on impressions made from behavioral information, the most consistently activated region is the dorsomedial PFC. Several studies have also identified the amygdala and ventromedial PFC as being critical in the updating of person impressions. The chapter concludes with a discussion of outstanding questions regarding the neural basis of forming impressions.