Abstract: Objective In non-small cell lung cancer(NSCLC)radiotherapy,probe target delineation and subsequent influence on target volume(TV)and exposed dose of normal tissues(NT)were based on PET/CT.Methods We selected 21 patients with NSCLC stage T3-4N₀M₀,and obtained TV and NT by CT images and PET/CT images,respectively.IMRT treatment plans were designed for PTVCT and PTVPET,respectively.We compared the deviation of two target volumes and exposed dose of normal tissues when target-volume-dose receives the clinical requirements.The NT′s parameters included Vx and MLD of lung,V40 of heart and maxdose of spinal cord.T-test and correlation analysis were used in the paper.Results TV of CT was greater than that of PET/CT in 85.7% cases,P=0.001(CTV),P=0.001(PTV)(statistically significant deviation).There was significant correlation between the target volume deviaton and the target volume,correlation coefficient(r)=0.96(GTV),r=0.82(CTV),r=0.61(PTV).The parameters in IMRTPET were optimizor in IMRTCT.P=0.017(V20),P=0.004(MLD)in lung and P=0.02(heartV40)in heart were statistically significant deviation.Conclusion PET/CT image has beneficial effect on target volume and normal tissues protection.