The skeleton is one of the preferential sites for metastases of solid tumors, and metastatic disease is the most common malignancy of the bone. Diagnosis and evaluation of skeletal metastases require more frequently a combined approach of different diagnostic methods. Between the currently available imaging modalities, a major role is devoted to two radionuclide functional techniques namely scintigraphy and positron emission tomography (PET) imaging. Both these techniques require the use of different radiopharmaceuticals. The aim of this paper is to review the most important radio-compounds that can be successfully used to detect and/or characterize bone metastases.