Objective: To optimize the semi-quantitative interpretation of 18F-FDG PET scans in the diagnosis of pancreatic carcinoma by retrospective analyzing different cutoff levels for the SUV, and to evaluate the usefulness of FDG PET-CT for the patients with pancreatic cancer.Methods: 151 patients with malignant and benign pancreatic lesions or normal pancreas were performed using an integrated PET-CT device.①Sixty-four patients (41 males, 23 females, mean age 63.5y) presented with suspected pancreatic carcinoma.The final diagnosis was made by histological and/or cytological analysis (n=23) and/or clinical-radiological follow-up for at least 6 months (n=41).55 patients had delayed imaging at the same time.②21 patients (23 lesions) with pancreatic metastases (16 males and 5 females, mean age 57.3y) were followed up by clinical-radiological at least 6 months.Primary lesions included 10 lung cancer, 3 renal cell carcinoma, 2 lymphoma, 1 breast cancer, 1 esophageal cancer, 1 gastric cancer, 1 cervical cancer,1 sarcoma and 1 malignant melanoma.13 patients (15 lesions) had delayed imaging.③ 32 patients (37 lesions) with pancreatic benign lesions or pancreatitis were followed up by clinical-radiological at least 6 months.34 patients underwent PET-CT examination showed 35 FDG uptake in the normal pancreas.These were confirmed by delayed PET-CT imaging and the other negative radiological examination.These patients were followed up for at least 6 months.66 patients included 36 males and 30 females (mean age 54.2y).37 patients had delayed imaging.The comparison between malignant and benign pancreatic lesions was completed using the ROC (receiver operating characteristic) analysis, and the area under the curve was calculated.The optimal cut-off value for SUV was determined.Results: The SUV for the malignant lesions ranged from 1.2 to 14.3 at the early imaging (n=87)and from 1.4 to 12.8 at the delayed imaging (n=70).The SUV for the benign lesions or normal pancreas ranged from 0.8 to 5.7 at the early imaging (n=72) and from 0.7 to 6.7 at the delayed imaging (n=37).This difference was statistically significant (P<0.05).The area under the curve was 0.9036 at the early imaging.Using a cutoff value of 3.0 for the SUV, PET-CT had a Youdens index of 0.69, sensitivity of 83%, specificity of 86% and accuracy of 84%.The area under the curve was 0.8788 at the delayed imaging.Using a cutoff value of 2.9 for the SUV, PET-CT had a Youdens index of 0.68, sensitivity of 93%, specificity of 76% and accuracy of 87%.Conclusions: The optimal cutoff value of FDG uptake to differentiate malignant from benign pancreatic lesions was 3.0.PET-CT examination had a higher diagnostic value.The SUV of delayed imaging could improve diagnostic sensitivity and accuracy.