The notion of Kresy Wschodnie till nowadays remains one of the most arguable matter and is not clearly determined among historians and politicians, that's why has a reflection in present and influences public and political life in modern countries. In the article the meaning of this territory is analised as well as its perception in collective conscience, use of Kresy Wschodnie in political plans by Polish parties, also in Polish public and political opinion in times of World War I and at the beginning of formation of independent Poland. Polish socio-political opinion during the World War I and at the beginning of formation of independent Poland, namely Second Polish Republic, reflected main views, concepts, plans of Polish parties and had practical value for determination of Polish borders. Kresy Wschodnie was considered by Poles as ancient Poland and according to them this native land was full of strong-willed, talented people, who glorified Poland. The Poles who lived on eastern lands and belonged to Russia after the division of Poland kept trying to restore the Polish state system. November and January uprisings in XIX century, intense work and formed political parties implied to join these lands to the future state of Poland. World War I gave hope to Poles for gaining autonomy and independence. Authority appeals to the Polish nation in Russia, Germany and Austria-Hungary were referred to Poles to support ruling establishment. Different foreign policy: pro-Russia and pro-Austria-Hungary; different ideological attitudes and directions did not stop Polish political forces from joining for creating their own state after Germany and Austria-Hungary made a Declaration of Independence for Kingdom of Poland in November 5, 1916, as well as Russian Provisional Government Appeal of acknowledgement of independent united Poland in March 1917. The appearence of independent Poland after World War I forced topical issues to be solved: to define eastern borders, status of Kresy Wschodnie, political attitude towards people on these lands. This matter had two main directions. Endecja was pro-Russia and considered Russia to be an ally in future war with Germany. The National Democracy programme meant restoration of Polish lands from 1772. This included western Ukrainian lands (Kiev region, Volyn, Podil, Galicia), some part of Lithuania and Belarus. However, proclamation of new rules of international life by American President Woodrow Wilson, which were supported by Entente countries, the policy of Left governments put conditions that Endecja agreed to the part of eastern territory defined by Treaty of Riga. The policy of land incorporation was aimed at making a country nationally similar and could become an ally to Russia. This explains why Endecja did not suggest maximum territorial programmer at the east and could compromise with Russia. Lots of scientists a political figure explained such position for negotiation at international level. According to Lefts forces regarding Kresy Wschodnie, namely Polish Socialist Party, and thier leader J. Pilsudski, Ukrainians, Belarusians and Lithuanians could form their own independent states, which would become a buffer between Poland and Russia. This would make an utmost interest of Poland. One more acceptable variant would work for Lefts if Poland created a federation with Ukraine, Lithuania and Belarus. Although, in theory it implied work within political parties. In practice first Left government wanted to preserve Polish state interests and provide rights for national minorities on eastern lands. Right forces that came to rule in 1923, changed the policy according to their point of view.