A 72-year-old man with right lower lobe squamous cell carcinoma of the lung—status, post resection—and prostate carcinoma was referred for restaging with whole-body PET using F-18 FDG. PET images, in addition to the presence of moderate hypermetabolic activity seen in the left lower paratracheal and bilateral hilar regions, revealed a large hypometabolic space-occupying lesion in the abdomen. The appearance of this lesion was highly suggestive of a pancreatic pseudocyst. Further review of a CT scan performed 3 years ago confirmed the presence of a pancreatic pseudocyst. However, this information was not available to the nuclear medicine physician at the time of the PET examination.