Previous research has suggested that the presence of schizotypal personality disorder may represent a risk factor for treatment failure in obsessive-compulsive disorder (OCD). Relying on a dimensional approach, the present study investigated whether the predictive importance of schizotypal personality is shared by all of its features to the same extent or whether it is confined to a subset of symptoms. Fifty-three patients underwent multi-modal cognitive-behavioral therapy with or without adjunctive antidepressive medication. Therapy response was defined as a 35% decline of the Y-BOCS total score. At baseline assessment, patients were asked to fill out the schizotypal personality questionnaire, the perceptual aberration scale and the Beck depression inventory. Stepwise regression analysis and group comparisons conducted with the schizotypal and depression scales revealed that elevated scores in the positive schizotypal scales, especially perceptual aberrations, were highly predictive for treatment failure. Responders to treatment and non-responders did not significantly differ on other variables or on scores in two scales which measured response biases. The study provides evidence that positive schizotypal symptoms are antecendents for treatment failure in OCD. It needs to be evaluated whether these at-risk individuals benefit from additional intervention, such as the adminstration of low-dose atypical neuroleptics and specifically tailored behavorial intervention.