The title of autokrator first appeared in the Rhomaian Empire (Byzantium). Translated as samoderzhets, it was taken up by Slavic countries that followed Rhomaian tradition. Taking as her starting point the indispensable 1935 work by George Ostrogorsky Autokrator and Samoderzhets, the author has analysed similarities and differences in the development of the title of samoderzhets in Serbia and Russia. Three phases have been analysed, of which the first two in more detail: the beginning of the use of this title; the development of the title and its significance; the diverging of the ways of Serbia and Russia. The first phase shows that the adoption of the title in both countries is preceded by both an increase of the country’s actual power and the improvement of its position among other Christian (Orthodox) countries. A significant difference appears in the second phase: Serbian kings have used the title of samoderzhets, but it was no longer in use after Stefan Dušan’s coronation as Emperor; after the fall of the Empire, Serbian rulers began to use it again. In Russia it was the other way around: the use of the title was more frequent after Ivan IV’s coronation. It seems that the title was mainly used in Serbia to underline independence where there was no obvious proof for it, and thus was not needed during the Serbian Empire, while Russian rulers, on the contrary, used it only when they had earned it through the actual power of their country. In the third phase both countries abandoned the Rhomaian model. Russia turned to Western models from the time of Peter I, while the development of Serbia was interrupted by its fall under Ottoman rule.