The role of (124)Iodine-PET/US Fusion technique is demonstrated in a 52-year-old woman with De Quervain's subacute thyroiditis. A small and adversely located lesion not detected by thyroid scintigraphy could be unambiguously matched with a hypofunctional PET finding. The presented case supports the clinical potential of PET/US Fusion technique in thyroid disease especially in small and uncertain findings.