Background: we investigated the value of 18F-FDG PET/CT for preoperative detection of lymph node(LN) metastasis and evaluation of tumor resectability in gastric cancer. Methods: This study included 156 gastric cancer patients who underwent surgery. The standardized uptake value (SUV) was calculated. Results: The rates of FDG uptake in the primary tumor were higher in the following parameters: AGC vs. EGC (85.5% vs. 43.6%, p < 0.001), tumor size = 3 cm vs. < 0.001), LN metastases in histology (86.8% vs. 46.1% p < 0.001). Patients with advanced and large tumor sizes and underwent non-curative surgery showed relatively high uptake rates in the local LN. When the SUV of the primary tumor was greater than 3.75, the sensitivity and specificity of PET/CT with regard to the diagnosis of metastatic LN were 73.5% and 74.5%. When the SUV was greater than 4.35 and the FDG uptake of LN was positive, non-curative surgery was predicted with a sensitivity of 58.8% and specifi city of 91.6%. Conclusions: A high FDG uptake rate and SUV of the gastric tumor was related to histologic positive LN and non-curative surgery.