Neuroendocrine tumors (NETs) constitute a heterogeneous group of neoplasms including carcinoids, pancreatic neuroendocrine tumors, pituitary tumors, medullary thyroid carcinoma and phaeochromocytomas. The symptoms and the outcome of NETs differ considerably between patients depending on several factors. By labelling tracers with a radioisotope, the tracer acts as a carrier to deliver the radioactivity to tissues expressing somatostatin receptors (SSTRs) and may be used for diagnosis and treatment. Several factors influence the selection of an appropriate therapeutic radioisotope. A longer physical half-life and low dose rate may be more effective for relatively indolent malignancies such as NETs. Radiolabelled targeted therapy is a fairly recent and promising modality for the management of patients with inoperable or disseminated NETs when conventional therapies fail.