Having emerged onto the stage of international relations ten years ago, independent Ukraine could not but affect them due to the magnitude of the transformation which it was undergoing since the breakup of the Soviet Empire. At the same time its relations with other states, particularly with the major powers, to a large extent influenced the course of its own nation-state formation. As this was the second attempt at state-building in Ukraine's history, the first one being a short-lived struggle for independence from Russia after the Bolshevik Revolution of 1917, the thesis aims to provide a comparative analysis of the two periods in which Ukraine pursued its goal of national statehood. It focuses on how and to what extent the latter was affected by external factors, above all by the policies of the two key players in international relations, Great Britain and the United States of America. Part I of the thesis examines the bilateral relations, political and diplomatic, between the two Western powers with Ukraine during the first period, namely from 1917 till 1921 when Ukraine was finally absorbed by Bolshevik Russia. Part 2 provides an account of these relations from the time Ukraine declared independence from the USSR in August 1991 until the end of 1994, a year in which the major stumbling-block to Ukraine's co-operation with the West, its possession of the nuclear arsenal inherited from the disintegrated Soviet Union, was removed and the two Western states in question alongside Russia signed a number of international agreements guaranteeing Ukraine's sovereignty. Finally, the comparative analysis of the two periods under consideration assesses the difference between the principles underlying relations of Great Britain and the United States with Ukraine at the end of World War I and in the early nineties and the ways these relations affected the process of nation-state formation in the Republic. The research is based on original sources and data. Although some of the primary sources, mainly relating to the first period, had been published previously in collections of documents, many of them are introduced and analysed for the first time. While a great number of monographic studies and journal articles have been written on Ukraine, the sphere of its international relations has so far not been properly explored. The thesis thus contributes to the general study of Ukraine's foreign relations and for the first time closely examines the interconnectedness between its state-building performance and external factors.