OBJECTIVE: The purposes of this essay are to describe the effects of bismuth breast shielding on radiation exposure of the breast and posterior chest wall and to present arguments for and against the use of breast shields. CONCLUSION: Breast tissue may receive substantial radiation doses during CT examinations. Bismuth shields effectively reduce breast exposure at the expense of increased noise and artifacts. Because bismuth shields reduce radiation transmission in all directions, posterior-to-anterior irradiation results in wasted exposure of posterior tissues. Similar breast radiation reductions can be achieved without shielding by globally reducing tube current. In general, more advanced methods of reducing exposure, including dose modulation and iterative reconstruction techniques, are superior if available.