Similarities between obsessive-compulsive disorder (OCD) and body dysmorphic disorder (BDD) have been described in terms of clinical presentation, comorbidity rates, treatment response profiles, and other features. This is the first study to compare insight in OCD and BDD measuring global insight and numerous components of insight. We compared insight in 64 adult outpatients with DSM-IV OCD and 85 adult outpatients with DSM-IV BDD using a reliable and valid measure (the Brown Assessment of Beliefs Scale [BABS]). BDD patients had significantly poorer global insight than OCD patients. BDD patients also had significantly poorer insight on the following components of insight: conviction that the belief is accurate, perception of other's views of the belief, explanation for differing views, willingness to consider that the belief is wrong, and recognition that the belief has a psychiatric/psychological cause. Poorer insight was significantly positively correlated with more severe symptoms of the disorder only in the BDD group.