False positive radioiodine uptake following thyroidectomy for differentiated thyroid cancer has been reported in some cases. A 57-year-old female patient was referred for ablative radioiodine treatment four weeks after undergoing total thyroidectomy for papillary thyroid carcinoma. Posttherapeutic I-131 scintigraphy showed uptake in the neck and large focus in the lower abdomen and pelvis. Pathology revealed a mucinous adenocarcinoma of the right ovary.