Nuclear medicine has a major and crucial role in the management of malignant tumors. With the developments toward molecular imaging and the advancement of equipment used for imaging particularly after combining the nuclear medicine instruments with morphologic modalities, it has even become a more integral part of management protocols. This role includes detection of malignant tumors, staging and restaging of the disease, early detection of recurrence, evaluation of the response to therapy, and prediction of the prognosis. Additionally, nuclear medicine is used in sentinel node identification and localization for biopsy to help plan the most suitable management for several tumors. This chapter discusses the important role of utilizing nuclear medicine techniques in the modern management of tumors. The commonly used and newly developed radiopharmaceuticals are presented.