Defects localized in the frontal sinus are difficult for surgical treatment, since there is a large number of anatomical variations in the structure of the naso-frontal canal and the sinus itself. With the development of endoscopic technology and paying attention to the modern tendency of minimal invasive surgery, new invasive approaches to reach frontal sinus, such as endoscopic approach according to Draf I—III and combined approaches were developed and put into practice. Objective — to summarize and to analyze the results of treatment of nasal liquorrhea with localization of the defect in the frontal sinus using endoscopic endonasal and combined intra-extranasal approaches. Material and methods. A retrospective analysis of a series of 43 cases of nasal liquorrhea with a frontal sinus defect being treated at the NMRCN Burdenko during the period from 2001 to 2017. To select access, a classification of frontal sinus defects according to their localization was developed. The analysis of demographic and clinical data of patients, as well as intraoperative and postoperative data analysis were done. Results. In the series of 43 patients, endoscopic endonasal approach was performed in 28 (65%) cases. Combined approach was performed at 15 (35%) patients. The success rate of plastic surgery with endoscopic endonasal approach was 86% (24 of 28), with combined approach — 93% (14 of 15). Conclusion. Endoscopic endonasal and combined approaches are the methods of choice for plastic surgery of defects of the skull base in the frontal sinus as they are effective and safe. The choice of approach depends on anatomical features of the frontal sinus and on the localization of defect.