Several shortcomings of the current psychodiagnostic manuals (DSM-IV, ICD-10) with respect to obsessive-compulsive disorder, such as the diagnostic parity of obsessions and compulsions and the deficient conceptualization of compulsions might artificially inflate the clinical prevalence of obsessive-compulsive (OC) symptoms in the course of schizophrenic disorders. Still, one cannot exclude on purely a priori grounds the possibility of a genuine coexistence of OC symptoms along with delusions in patients with schizophrenia. the aim of the present study was to provide a contrastive conceptual analysis of typical features of obsessions versus those of delusions and correlatively of compulsions versus delusionally-motivated repetitive behaviours, supplemented by four relevant vignettes as clinical tests of its adequacy. Although preliminary, the results of our conceptual and illustrative analyses suggest that General Psychopathology can afford the conceptual resources for the accurate differential diagnosis obsession/compulsions from delusions/delusionally-motivated repetitive behaviours. in turn, this would provide a more solid clinical ground for the investigation of the epidemiology and the pathophysiology of OC symptoms in schizophrenic disorders.