Emotions can have both enhancing and impairing effects on various cognitive processes, from lower (e.g., perceptual) to higher level (e.g., mnemonic and executive) processes. The present article discusses emerging brain imaging evidence linking these opposing effects of emotion, which points to overlapping and dissociable neural systems involving both bottom-up and top-down mechanisms. The link between the enhancing and impairing effects is also discussed in a clinical context, with a focus on posttraumatic stress disorder (PTSD), where these opposing effects tend to co-occur, are exacerbated, and are detrimental. Overall, the present review highlights the need to consider together enhancing and impairing effects of emotion on cognition in studies investigating emotion–cognition interactions.