This paper, extensively employs articles and studies by Lithuanian historians of the period that are regarded as a heritage of Lithuanian historiography, examines the national ideas and concepts of Lithuanian historians and concentrates on Lithuanian-Polish discussion on questions such as: How they understood nationalism? How they analysed and evaluated political programs for the re-establishment of statehood of Lithuania, i.e. for political autonomy of Lithuania and for Polish-Lithuanian federal state? What kind of arguments they used against the Polish territorial claims toward Vilnius and its district? What are the main features of Klimas’ concept of nationalism?