In clause(article) features of territory of the countries the Commonwealths of Independent States (CIS), and also number and structure of the population are shown. The special attention is inverted on studying of demographic processes in these countries – birth rate, death rate of the population. The author has noted, that in the end the XX-beginning of XXI century reduction in a level of birth rate, increase of death rate, reduction of life expectancy, especially man's population of the countries CIS was observed. However the natural loss and reduction of a population were characteristic for Byelorussia, Moldova, Russia and Ukraine.