To evaluate the value of positron emission tomography (PET) imaging with 18 F-FDG in differentiation of benign and malignent pancreatic mass. 12 patients with pancreatic occupying lesion diagnosed by ultra sond or CT/MR including 7 pancreatic cancer and 5 pancreatitis underwent 18 F-FDG PET imaging. Visual interpretation and semiquantitative analysis by calculating the tumor/liver ( T/L ) ratio based on ROI were performed on attenuation corrected images. 9 positive findings were detected. Among them

7 were confirmed to be cancer

but the other 2 were mass-forming pancreatitis. Final diagnoses of the 3 patients with negative findings were confirmed to be pancreatitis. The mean T/L ratio was 2.58±0.95 in pancreatic cancer

significantly higher than that in pancreatitis (1.29±0.87) ( p =0.037). With a T/L ratio cutoff value of 1.5

all 7 cancer patients were correctly categorized. However

one pancreatitis had T/L ratio higher than 1.5. 18 F-FDG PET imaging was a potential reliable method in differentiating benign or malignant pancreatic mass with high negative predictive value

but the specificity was limited. Semiquantitative analysis may improve the accuracy of the diagnosis.