The results of neuropsychological-cognitive investigations in patients with obsessive-compulsive disorder are presented in a meta-analysis. The analysis differentiates between intelligence, attention and concentration, memory executive functions, and visual-spatial and visuo-constructive performance. Changes in intelligence are only rarely manifest in obsessive-compulsive patients, and if so, principally in the visuo-constructive field, possibly including abstract-logical processes of thinking. Similarly, they are largely normal in functions of attention and verbal memory; only complex study designs reveal deficits in comparison to control subjects. Obtained deficits in visual memory should be interpreted as being likely due to deficient visuo-perceptive and visuo-constructive performance. Executive functions have not been studied in depth and are unimpaired in most investigations. Visuo-constructive problems are observed most frequently and might best be attributed to problems in Gestalt perception. It has to be pointed out that up to now techniques and designs of investigation are, in the majority of studies, imperfect and that it seems necessary to consider the existence of subgroups of obsessive-compulsive patients with differing degrees of impairment. Prognosis and evaluation of patients with obsessive-compulsive symptomatology depend considerably on their insight into the irrelevance of their behavioural patterns and on the contents of their predominant thoughts and actions. Transferring the deficit patterns to the brain level points to (a) right hemispheric damage and (b) damage in the frontostriatal system.