ENThe article analyzes the specificity of the use of titles of Polish-Lithuanian and Russian monarchs in the diplomatic correspondence of the Grand Duchy of Lithuania and Moscow State at the end of the XVI century. The article emphasizes the communicative aspect: the differences in the use of titles in relation to the addresser and to the addressee of diplomatic messages and letters are revealed taking into consideration the corresponding elements of the formular - the intitulation and the inscription. In this regard, special emphasis is paid to the titles of tsar and samoderzec that are given central positions in the title of the Russian sovereign at the end of the XVI century, but are consistently ignored by the Polish-Lithuanian political elite. As the study shows the use of the monarchs' titles in the diplomatic correspondence of the Grand Duchy of Lithuania and the Moscow State outgrows the framework of a purely etiquette function turning into a tool of political manipulation.