Cholecystokinin (CCK) is a polipeptyde having many functions in digestive system (regulating motor activity and secretion) and acting as a neuromodulator in central and peripheral nervous systems. Recent research shows that CCK increases insulin and glukagon secretion and activates hypothalamo- pituitary- adrenal axis. It also plays a role in cardiovascular system (CCK has a positive inotropic effect). The aim of this study is to show some recent knowledge in the subject of CCK structure and its function in human body.