A review on the study of properties of the platinum clusters in zeolites. The main attention is paid to the conditions of preparation affecting the valence state of platinum and size and location of platinum clusters in zeolites. These factors, together with the electronegativity of zeolite matrix (varied by the presence of different alkaline cations and Si/Al ratio), control the course of catalytic reactions as it is shown in several model examples. The reduction of nitrogen monoxide by carbon monoxide is discussed as a special case.