Obsessive-compulsive symptoms have been associated with different types of damages or dysfunctions in the brain. However, the accumulated evidence on obsessive-compulsive symptoms among patients with a primary brain tumor is so far based on case reports only. The study population consisted of 59 neurosurgical patients with a primary brain tumor. One preoperative and two postoperative assessments for the level of obsessionality were done with the Crown-Crisp Experiential Index (CCEI)-instrument. Mean obsessionality scores increased significantly among the patients with a tumor in the left anterior region of the brain measured at 3 months after operation, especially in women, compared to the patients with a tumor in other regions of the brain. The level of obsessionality seemed to increase immediately after operation among patients with a primary tumor left anteriorly in the brain. This increase may be linked with the lesion caused by the tumor itself or the neurosurgical operation.