Abstract: Gastrin is a kind of braingut peptide and present in both central nervous system (CNS) where it plays the roles of neurotransmitter or neuromodulator and in some peripheral tissues, mainly in gastrointestinal tract, where it may be considered as a hormone. Some researches revealed that most of the effects of gastrin were results from the specific interaction with cell Cholecystokinin-B (CCK-B, formerly CCK-B)/gastrin receptors. CCK-B/gastrin receptors have recently found increasing interest as targets for nuclear medicine applications. A high incidence of CCK-B receptors has been found in human samples of medullary thyroid cancer (MTC), small cell lung cancer (SCLC), stromal ovarian cancers, and also in vivo in gastrointestinal neuroendocrine tumors. Radiolabeled gastrin analogues have high specific affinity to receptor in Cholecystokinin-B/gastrin receptors positive tumor. This article reviews about gastrin and its analogues for cancer imaging and therapy.