Radioiodine is often seen to accumulate within breast tissue in patients with differentiated thyroid cancer. Although the risk of secondary breast malignancy in patients with differentiated thyroid cancer treated with radioiodine is controversial, the identification and reduction of this uptake is prudent to minimize the radiation absorbed dose to the breast tissue. This article reviews the literature describing the etiology, frequency and patterns of radioiodine uptake in breast tissue. Approaches and techniques to help minimize the radioiodine uptake in lactating and nonlactating breasts are presented.