Although radioiodines are widely used to localize metastatic differentiated thyroid cancer (DTC), 99mTcO4 also can be used because it is a substrate for the sodium-iodide symporter protein. The use of 99mTcO4 has advantages over radioiodine, namely, easy availability, dispensability of iodine restriction, and early imaging time. However, its low sensitivity precludes its practical application. Scintigraphic detectability of DTC using sodium-iodide symporter substrates is related to the serum TSH levels. Here, I report a case with multiple metastatic lesions of DTC that were detected upon TSH-stimulated 99mTcO4 scintigraphy, but not with non–TSH-stimulated scintigraphy using the same tracer.