Olfactory groove meningiomas are benign tumors that grow along the midline floor of the anterior cranial fossa, from the cribiform plate to tuberculum sellae, and account for 4-10% of the intracranial meningiomas; they are benign and rather slow growing tumors. Women are more affected than men. The basic treatment of olfactory groove meningiomas is surgical. Complications of surgical treatment occur in 1/3 of the patients in the course of the long-term follow-up, the most frequent of which are cerebrospinal fistula, epileptic seizures, postoperative hygromas, pneumonias, embolism, whereas the lethal outcome is reported in 3% of the operated patients, reaching even 11% in the patients with extremely large olfactory groove meningiomas. The aim of the paper was to determine whether the presence of peritumoral edema in the patient having olfactory groove meningioma can affect the more frequent occurrence of postoperative complications, and whether the preventive removal of the edematous parts of the frontal brain lobe covering olfactory groove meningioma can reduce the rate of complications and lethal outcome. The paper included 35 patients (24 women and 11 men) operated for olfactory groove meningioma. The tumor and edema volumes were calculated and the results were correlated with the occurrence of postoperative complications and lethal outcome. Of great importance was the analysis of preventive removal of malatic and edematous parts of the frontal lobe of the brain. Surgical treatment of large olfactory groove meningioma accompanied by high degree of peritumoral brain edema is associated with high risk of complications, primarily with reactive edema and hemorrhage. The preventive removal of malatic and edematous parts of the frontal lobe of the brain is a useful operative procedure which significantly reduces the postoperative risk of edema, hemorrhage and lethal outcome