Introduction. In connection with the evolvement of expanded endoscopic approaches to remove tumors of the base of the skull, modern literature focuses on the results of radical surgery. There are few works devoted to defects in the base of the skull during removal of the tumor and their plastic closure. The purpose. Analysis of a series of cases of endoscopic endonasal removal of a tumor of the base of the skull with simultaneous plastic surgery, development of a convenient classification of defects with practical recommendations. Material and methods. Retrospective analysis of 50 cases of removal of tumors of the base of the skull with simultaneous plastic surgery of the defect of the base of the skull. The results of plastic surgery after removal of the tumor in the early and late postoperative period were evaluated. A literature review was conducted to compare the data obtained with the results of other studies. Results. After removal of the tumor, all 50 patients underwent simultaneous plastic surgery of the defect. The choice of technique and plastic materials for closing the defect did not depend on the degree of malignancy of the removed formation (p=0.174; criterion χ2). The histological structure of the tumor and subsequent radiation therapy in the case of malignant tumors were did not affect the risk of developing of liquorrhea in the postoperative period (p=0.221; Fisher’s exact test). Based on the results obtained, we developed our own classification of defects in tumors of the base of the skull, taking into account the size, localization and plastic materials used. Conclusions. For intracranial spread of the tumor of the nasal cavity and paranasal sinuses, the removal of the tumor by endoscopic or combined approach with simultaneous plasty of the skull base defect is indicated. The choice of plastic materials and the method of plasty depends on the location, size of the defect, the degree damage to the surrounding tissues and the dura matter by tumor. The effectiveness of the plasty does not depend of the histological structure of the tumor and subsequent chemo- and radiation therapy.