Herein, we report a case of a 19-year-old man with multiple endocrine neoplasia type 2B (MEN2B) and medullary thyroid carcinoma (MTC) diagnosed when he was 12 years of age. The patient had previously undergone total thyroidectomy, cervical radiotherapy, and chemotherapy. He progressed with known bone, pulmonary, and lymph node metastases and was scanned with ¹⁸F-fluoride (¹⁸F-NaF) and ⁶⁸Ga-dotatate whole-body positron emission tomography/computed tomography (PET/CT) for metastatic disease monitoring.We found that the MTC bone metastases and soft tissue calcified metastases were better characterized on ¹⁸F-NaF PET/CT than on ⁶⁸Ga-dotatate PET/CT. This case illustrates that the ¹⁸F-NaF PET/CT could be helpful not only to the detection of bone metastases but also to the detection of calcified soft tissue metastases in patients with MTC.