Background. Overcoming radioresistance is an important problem in radiation oncology. Therefore, the development of new approaches to modeling the radiosensitivity of tumors in cancer patients becomes relevant and important. Cyclooxygenase-2 (COX-2) inhibitors are new agents for radiomodification in various radiation therapy schemes, the use of which slows down angiogenesis by suppressing the activity of the COX-2 enzyme. Purpose. To determine the content of indicators of radioresistance: vascular endothelial growth factor (VEGF), COX-2, prostaglandin E-2 (PGE-2) in the blood serum of patients with non-small cell lung cancer (NSCLC) and changes in their levels with different schemes of radiation therapy (RT). Materials and methods. 36 patients with NSCLC were examined and treated, who were divided into four groups: RT (the first group – 16 patients), RT with the COX-2 inhibitor – ranselex (the second group – 9 patients), RT with ranselex and cisplatin (the third group – 5 patients ) and RT with cisplatin (fourth group – 6 patients). The patients received a course of radiation treatment using a Clinac 600C linear accelerator. The classical fractionation mode was used, the total focal doses were 60–66 Gy. Cisplatin was prescribed at 30 mg/m2 per week up to a total dose (SD) of 200 mg, the COX-2 inhibitor Rancelex® at a dose of 100 mg per day (active substance – celecoxib). The levels of VEGF, COX-2, and PGE-2 in the blood serum of patients with NSCLC were determined by enzyme-linked immunosorbent assay (ELISA) before and after treatment. Results. The level of the angiogenesis marker VEGF after treatment in the group with RT decreases by 1.46 times, in the group with the combined action of RT and ranselex – 2.4 times, in the group with the combined action of PT, ranselex and cisplatin – by 3.7 times, and in the group with the combined effect of RT and cisplatin, it decreases by 1.1 times. The greatest decrease in the level of VEGF is observed with RT in combination with ranselex and cisplatin, which indicates a more effective enhancement of the antiangiogenic effect. Conclusions. It has been proven that with various schemes of RT using the COX-2 inhibitor – ranselex and cisplatin in patients with NSCLC, there is a decrease in the radioresistance markers PGE-2 and COX-2, the angiogenesis marker – VEGF, which indicates that the effect of radiomodification on the angiogenesis process is most pronounced in the combined actions of RT and both radio modifiers. The use of COX-2 inhibitors as radiosensitizers in combination with RT provides a new opportunity to increase tumor radiosensitivity.