BACKGROUND: Obsessive-compulsive disorder (OCD) is associated with marked anxiety, which triggers repetitive behaviours or mental rituals. The persistence of pathological anxiety and maladaptive strategies to reduce anxiety point to altered emotion regulation. The late positive potential (LPP) is an event-related brain potential (ERP) that reflects sustained attention to emotional stimuli and is sensitive to emotion-regulation instructions. We hypothesized that patients with OCD show altered electrocortical responses during reappraisal of stimuli triggering their symptoms. METHOD: To test our hypothesis, ERPs to disorder-relevant, generally aversive and neutral pictures were recorded while participants were instructed to either maintain or reduce emotional responding using cognitive distraction or cognitive reappraisal. RESULTS: Relative to healthy controls, patients with OCD showed enhanced LPPs in response to disorder-relevant pictures, indicating their prioritized processing. While both distraction and reappraisal successfully reduced the LPP in healthy controls, patients with OCD failed to show corresponding LPP modulation during cognitive reappraisal despite successfully reduced subjective arousal ratings. CONCLUSIONS: The results point to sustained attention towards emotional stimuli during cognitive reappraisal in OCD and suggest that abnormal emotion regulation should be integrated in models of OCD.