Abstract: ¹³¹I whole-body scan and SPECT imaging in patients with differentiated thyroid cancer can provide information regarding metastasis and prognosis, and assist in treatment planning. However, false positive uptake, which is not residual thyroid tissue or metastases, is sometimes encountered. Unless recognized as a false positive, ¹³¹I uptake may result in diagnostic error and lead to administration of an unnecessary therapeutic dose. This review discussed various possibilities of false positive uptake on ¹³¹I whole-body scan, as well as the underlying causes and mechanisms.