Aim of our paper is to review the most important radio-compounds that can be successfully used to detect and/or characterize bone metastases. From a didactic point of view, we made a distinction between two main categories , the first allowing to individuate bone's reaction (osteotropic agents), the second trying to detect metastatic tumor cells (oncotropic agents). A wide description of the most diffuse Tc-99m diphosphonates , including analysis of uptake mechanisms and pharmacokinetics, is followed by a brief report on pathophysiological premises to the clinical use of F-18 fluoride and of specific (radioiodine, radiolabeled somatostatin or cathecolamine analogues) or non specific, as Tc-99m sestamibi, F-18 fluorodeoxhyglucose, F-18 choline, F-18 thymidine) oncotropic agents. At the end, the possibility to use diagnostic radiotracers to act both in recruiting patients with bone metastases undergoing radionuclide therapy and for their dosimetric evaluation is also discussed.