ENA separate Department of the History of the Church in Poland was founded at the Faculty of Theology of the Jagiellonian University in Kraków in 1920 (1919) to operate beside an older Department of the History of the (Common) Church until the department was forced out of the University in 1954. Over the period of 35 years the Department was headed by two exquisite scholars with exceptionally broad research horizons (both with respect to the range of topics and chronology and history): a medievalist Rev. Jan Nepomucen Fijałek (1864-1936) and his disciple, specialist in modem history, Rev. Tadeusz Glemma (1895-1958). In the publications of the latter the issue of Lithuania is practically vestigial. Apart from a certain number of entries in the German Lexicon für Theologie und Kirche and an extensive index to the "Kodeks dyplomatyczny katedry i diecezji wileńskiej", developed with Adam Vetulani, other lithuanica in the published works of Rev. T. Glemma involve individual paragraphs or fragments in the synthetic studies on the general history of Catholicism in the Republic of Both Nations in the 16th and 17th centuries. The case of Rev. J.N. Fijałek is quite different. Among over two hundred printed titles, present in his bibliography, only under a score refer to Lithuania and religious relations there, yet these include the studies that deserve to be called fundamental for these issues. Among them, an exceptionally extensive study "Kościół rzymsko-katolicki na Litwie.Uchrześcijanienie Litwy przez Polską i zachowanie w niej języka ludu po koniec Rzeczypospolitej" (1914, 1987) needs to be mentioned first, followed by such dissertations as "Średniowieczne biskupstwa Kościoła Wschodniego na Rusi i Litwie" (1896-1897), "Biskupstwa wołyńskie Polski i Litwy w swoich początkach w. XIV/XV" (1911), "Opisy Wilna aż do połowy XVII wieku" (1923), "Kościół rzymsko-katolicki w Inflantach pod władztwem polskim" (1924) or "Los unii florenckiej w Wielkim Księstwie Litewskim za Kazimierza Jagiellończyka" (1934). However, the most significant contribution of Rev. Fijałek into the study of the history of Lithuania and Catholic Church there involves the Kodeks dyplomatyczny katedry i diecezji wileńskiej, developed in collaboration with Władysław Semkowicz, intended to cover the entire period between 1387 and 1580. Due to some unfavorable circumstances only the first volume of this work was published (for the years 13 87-1507) while the second one (covering the years 1508-1580) is still awaiting publication. The materials for this volume are stored at the Biblioteka Naukowa PAU and PAN in Kraków.