In this study, we investigated whether an indication for [18F]FDG-PET/CT to detect FDG-avid PD could be derived more precisely using the extent of MLNs (number of MLNs or LNR) and serum Tg, and whether the diagnostic performance of PET/CT could be improved by combining the extent of MLNs and serum Tg in patients with papillary thyroid cancer (PTC). Here, TG is linked to thyroid gland papillary carcinoma.