The literature on capacitive deionization (CDI) of water is discussed. The CDI is a new method of water desalination which consists of pumping water to be deionized between highly disperse carbon electrodes with a certain potential difference applied to these electrodes. The CDI is characterized by the lower expenditure of energy as compared with the other desalination methods. Different modifications of CDI are considered such as membrane capacitive deionization (MCDI), CDI with redox reactions on electrodes, and CDI with flow-through electrodes. The dependence of CDI on the porous structure of electrodes, the size of hydrated ions, the type of carbon used for electrodes, the electric double layer capacitance, the presence of functional groups, the wettability of electrodes, the pH, and other factors is considered. The problems of the production of pure drinking water and also of the degradation of electrodes are discussed. The use of CDI in practice is described.