So-called border states emerged one after another in the territories of the former tsarist state under the conditions of the Revolution of 1917 and the civil war that followed it. The birthdays of the following states are important from the standpoint of this article: Estonia on 24 February 1918, Abkhazia on 11 May 1918, and Georgia on 26 May 1918. The Georgian Democratic Republic annexed its neighbouring country Abkhazia, where the Estonian villages Salme, Sulevi, Upper- and Lower-Linda, and Estonia were located, in the summer of 1918. Soviet Russia signed a peace treaty with the Republic of Estonia in Tartu on 2 February 1920 and with the Georgian Democratic Republic in Moscow on 7 May of that same year. Both agreements also included articles on opting. This article considers present day arguments among the eastern diaspora of Estonians, primarily Estonians living in Abkhazia, on the subject of the question of citizenship, which has revolved primarily around the clauses on opting in the Tartu Peace Treaty. In recent years, Abkhazia’s Estonians have been a vivid standard, on the example of which to discuss the possibilities for interpreting the clauses on opting in the Tartu Peace Treaty signed between Estonia and Russia. Yet the paradox lies in the fact that the Tartu Peace Treaty could not actually apply to the opting of Abkhazia’s Estonians, since Abkhazia was not part of Russia at the time when the agreement was signed and the Tartu Peace Treaty did not make provisions for issues regarding the opting of individuals from other countries that were not party to the agreement. Abkhazia was part of the Georgian Democratic Republic at that time. Estonia had diplomatic relations with Georgia, and Abkhazia’s Estonians could apply for Estonian citizenship through the mediation of the Estonian consulate located in Tbilisi, which is indeed what hundreds of Estonians did. While the Estonian authorities have in recent years started recognising the Estonian citizenship by birth of the descendants of these individuals, the citizenship by birth of those people who are from the Estonian villages of Salme and Sulevi in the north-western part of Abkhazia still continues to be left unre­cognised. The article demonstrates that although these villages belonged to a neutral zone according to the Moscow Peace Treaty, it was still part of the Georgian Democratic Republic, for which reason the Estonian citizenship by birth of the descendants of the residents of those villages who opted for Estonian citizenship should be recognised. The article also considers citizenship questions of Estonians who remained in the Soviet Union in the 1920s and 1930s, which the Estonian and Soviet sides interpreted very differently. Both the Republic of Estonia and the Soviet Union considered Estonian citizens who remained in the Soviet Union, and who later adopted Soviet citizenship, to be their citizens. This was essentially dual citizenship, although the citizenship laws of neither country permitted dual citizenship.