The subject of this paper is in connection with the establishment of Czechoslovakia the Slovak question at the Paris Peace Conference in 1919-1920. The essay is based on the approach that the conception of this issue is not only a matter of internal significance, ie only for Czechoslovakia itself and the Czech and Slovak people, as the majority of professional studies are oriented. The solution of this issue was very important also in terms of stability of the forming international system after the First World War. After a clear historical recapitulation of the development and formation of the Czechoslovak state idea, attention is paid to discussing the establishment of Czechoslovakia and, in this context, especially the Slovak issue at the Paris Peace Conference in search of the optimal concept. The researched issue is affected in two interconnected levels. The first is recognition of the existence of Czechoslovakia as a state and, together with that, the second recognition of the territorial scope of that state with a focus on Slovakia.