Because of the heterogeneity of obsessive-compulsive disorders (OCDs) and their co-occurrence with anxiety disorders, we investigated the prevalence, severity, and correlations between obsessive and compulsive symptoms reported by patients diagnosed with OCD or generalized anxiety disorder (GAD).A retrospective study was conducted in 2 groups of patients: 76 patients diagnosed with OCD [F42 according to the 10th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10)], and 186 patients diagnosed with GAD (F41.1 according to ICD-10), who had presented for therapy at the day ward. The Symptom Questionnaire "O," based on the Symptom Checklist 90-Revised (SCL-90-R) questionnaire, was used to assess obsessive, compulsive, and anxiety symptoms. The analysis took into account the impact of sex and the presence or absence of cognitive dysfunction (as assessed using the Bender Benton Visual Retention and Bender-Gestalt tests) on the associations being investigated.We observed that obsessive and compulsive symptoms were more prevalent and more strongly expressed in the group with OCD than in the group with GAD. However, almost all patients with GAD (94%) confirmed the presence of some obsessive-compulsive symptoms. The study revealed differences in correlations with obsessions and compulsions between the OCD and GAD groups. In the group with OCD, no significant correlation between the severity of obsessions and compulsions was identified, whereas in the group with GAD, a significant positive correlation was found between the severity of those symptoms. In both the GAD and OCD groups, a greater intensity of obsessive-compulsive symptoms was accompanied by an increase in the severity of anxiety symptoms (with this effect noted to a greater extent with obsessions than compulsions).The study revealed that patients with GAD often have coexisting obsessive-compulsive symptoms, which may not be identified during routine psychiatric examination. Obsessive-compulsive symptoms observed in patients with GAD may show a different structure than obsessive-compulsive symptoms in patients with OCD. The results of this study suggest that compulsions are more specific for the diagnosis of OCD than obsessions. Compulsions, such as counting related to the need for order and symmetry, may be associated with some cognitive dysfunctions and male sex, a finding that requires further research.