Pediatric differentiated thyroid cancer (DTC) patients frequently present with lymph node and/or distant (lung) metastases. Such patients warrant an aggressive treatment consisting of surgical removal of all surgically accessible local metastases as well as further treatment with one or more courses of radioiodine therapy (RAI). It is still a subject of debate in literature how much I-131 should be administered to pediatric patients. Patients can either be given a fixed (possibly body weight adjusted) activity or a dosimetry based activity, which is often considerably higher.