Based on the analysis of Medieval Moldavian and Rumanian sources and works, the Old-Rus' population of the Carpatho-Dniestrovian region, the Rusins and the area of their settlement before the beginning of Vlach colonization, is analyzed in the article. This is confirmed by given toponyms and anthroponyms. In fact, many of them derive from the root "rus". The contribution of the Rusins to the formation of the Moldavian ethnos and statehood is underlined.