The paper considers the place of international migration in the various theoretical demographic structures (research areas, theories, concepts that are combined in the general concept named “demographic theory”) and takes into account its evolution.  In this theory, the demographic evolution itself largely due to the changing of role and place of international migration in the demographic development of the world and in some individual states. Special attention is paid to the general theory of population, the classical theory of demographic transition and the concepts of demographic transition. Also the paper gives brief description of the modern trends of international migration of population and shows increasing importance in the demographic development of immigration and emigration countries.