Although a dysfunctional prefrontal-striatal system is presupposed in obsessive–compulsive disorder (OCD), this is not sustained by neuropsychological studies. The aim of this study was twofold: (i) to investigate the cognitive deficits in patients with OCD compared to matched healthy controls; and (ii) to relate cognitive performance to clinical characteristics in patients with OCD. In this study, 39 patients with primary OCD according to Diagnostic and Statistical Manual, fourth edition criteria were compared to 26 healthy control subjects on a battery measuring verbal memory and executive functioning. Patients with OCD showed slowed learning on the verbal memory task and made more errors on the Wisconsin Card Sorting Test. Errors were failures to maintain set, which were related to severity of OCD symptomatology. The results show that patients with OCD have cognitive deficits. The authors hypothesize that these deficits may be interpreted by attentional deficits caused by a dysfunctional anterior cingulate cortex.