The study aims to describe one of the key and crucial events in the national history of modern Romania from the Romanian historiography's perspective. The author analyses the creation of a unitary state as a result of the unification of the Romanian Principalities of Moldova and Wallachia in 1859 under the leadership of Alexandru Ioan Cuza, who was elected as the ruler in each of those regions. This research provides valuable information on the issue of the Romania-Russia relations in the period of 1858–1862, when according to the Paris Convention of 7/19 August 1858 objective external conditions were created not only for the unification of the Romanian principalities, but also for the administrative reorganization and expansion of independence of the unitary Romanian state. The unification of the Romanian principalities, which in foreign policy terms was accompanied by a clash of interests of major powers (the Austrian, Ottoman, Russian Empires, Great Britain, and France), took place in those specific conditions that were not suitable for Russia's positions in Southeastern Europe and the Balkans. Nevertheless, the historiography does not question the role of Russian foreign policy as a factor that contributed to the international recognition of the young Romanian state, as well as the significance of the diplomatic activities of the Russian consuls in Bucharest and Jassy. That is why the introduction of Russian diplomatic reports that reflect the attitude of Russian consuls to Prince Cuza's policy and their connection with the Romanian elite is still a crucial task for historiography.