We report herein a case of follicular thyroid adenoma with an eggshell calcification presenting as an intensely hypermetabolic lesion on combined 18F‐fluorodeoxyglucose whole‐body PET and CT (18F‐FDG PET/CT) performed for staging work‐up in a 68‐year‐old woman who had undergone distal gastrectomy with Billroth II anastomosis for early gastric carcinoma. The mass was intensely hypermetabolic (SUVmax = 21.3 g/mL) on combined 18F‐FDG PET/CT, hypoechoic with an interrupted eggshell calcification on gray‐scale ultrasonography (US), and showed intranodular vascularity on power Doppler US. Follicular adenoma should be considered in the differential diagnosis of a mass with an eggshell calcification on US and intense hypermetabolism on 18F‐FDG PET/CT. © 2009 Wiley Periodicals, Inc. J Clin Ultrasound, 2010