Objective: In this study, we investigated the differences and similarities between bipolar disorder (BD) positive and BD negative obsessive-compulsive disorder (OCD) groups in terms of clinical characteristics and the affective temperaments. Patients and Method: Forty-four patients admitted to Bakirkoy Prof Dr. Mazhar Osman Hospital of Psychiatry and Neurology with the diagnosis of OCD were enrolled to the study. Patients were assessed by interview with patients (SCID I), applying sociodemographic form, Hamilton depression scale (HAM-D), Yale Brown OCD scale(Y-BOCS), and TEMPS-A affective temperament questionnaire. Results: The results showed significantly high rates of BD comorbidity (38.6), especially bipolar II, in patients with OCD. Seasonal course of OCD was prominent in patients with BD comorbidity (70%). The number of lifetime major depressive episodes and hospitalization rate was also higher in BD comorbid patients. Depressive (23.4%), anxious (17.6%) and cyclothymic (11.8%) temperament was predominant among bipolar OCD patients. There were no significant differences in scores of the affective temperaments between bipolar and non-bipolar OCD groups. Conclusion: We conclude that there are obvious clinical influences of bipolar disorder on OCD patients. Affective temperamental differences should be investigated on large samples in the bipolar and non-bipolar OCD patients.