Classified according to lymphatic, mesothelial, enteric, or urothelium origin, mesenteric cysts may be asymptomatic or present with abdominal pain from pressure effects on adjacent organs. They commonly demonstrate dense marginal calcification on CT. A 62-year-old gentleman was referred for PET/CT for initial staging of nonsmall cell lung carcinoma. Incidental note was made of a cystic mass with dense marginal calcification in the small bowel mesentery consistent with a mesenteric inclusion cyst. This lesion did not accumulate F-18 fluorodeoxyglucose (F-18 FDG). Mesenteric cysts are rare benign intra-abdominal lesions that may be identified on PET/CT that should not be mistaken for calcified treated metastatic disease.