Use of F-18 fluorodeoxyglucose positron emission tomography (F-18 FDG PET) in patients with known thyroid cancer is well documented, but the role of this imaging modality in the initial workup of a thyroid nodule has not been defined. The incidental finding of a hypermetabolic focus in the thyroid on F-18 FDG PET in patients with a variety of primary malignancies is reported. Based on the authors' literature search, this is the first documented case of a thyroid cancer resulting from papillary carcinoma detected in a patient with a history of non-Hodgkin lymphoma.