Abstract: Objective To provide the imaging evidence for the clinical diagnosis and differential diagnosis of advanced gastric cancer（AGC） and primary gastric lymphoma（PGL） by comparing their images of ¹⁸F-FDG PET/CT. Methods Pathology-confirmed ¹⁸F-FDG PET/CT findings in 34 AGC patients and 30 PGL patients were retrospectively analyzed.The revealing rate of CT and FDG uptaking and intensity for gastric cancer,the SUVmax and THKmax of gastric cancer,and the infiltration of adjacent lymph nodes were observed. Results FDG showed AGC in 30 patients（30/34） and PGL in 28 patients（28/30）.After the effect of THK_max was excluded,the SUV_max of ANHL was significantly higher than that of MALT and AGC（15.83±7.51 vs 6.07±4.40 and 9.81±5.17,P＜0.05）.Cross validation analysis showed that the accurate classification rate for ANHL and AGC reached 70% and 74% respectively when the SUVmax and SUV_max/THK_max threshold values were 15.87±1.76 and 7.62±0.76 respectively.No significant difference was found in the THK_max of MALT,ANHL and AGC（（2.02±0.88）cm,（2.40±1.31）cm,（2.27±0.81）cm,F=0.434,P=0.650）).Abnormal CT findings included adjacent gastric infiltration（ANHL,n=2;GC,n=8） and secondary gastric dilatation（ANHL,n=1;GC,n=4）. Conclusion SUV_max and SUV_max/THK_max contribute to the diagnosis and differential diagnosis of ANHL and AGC.CT can provide the valuable supplemental information for their diagnosis and differential diagnosis.¹⁸F-FDG PET/CT plays an important role in the diagnosis and differential diagnosis of PGL and AGC.