The purpose of this article is to acquaint the reader with the methods and research tasks of a recently developing subdiscipline of language studies known as Kitab studies. The aim of Kitab studies is to research the manuscripts of the Tartars (Muslims) of the Grand Duchy of Lithuania, some of which are translations from Arabic and other languages used in the world of Islam, such as Turkish or Persian, whereas others are adaptations of Old Polish Christian texts in the spirit of Islamic exegesis. The first manuscripts were written in mid-16th century and are unique in that the (Old) Polish and (Old) Belarussian languages were written in a specially adapted Arabic alphabet. Although the 16th century original texts have not survived until today, many and various copies have been preserved, and today they constitute a valuable basis for Kitab studies. The most valuable manuscripts include the copies of the first translation of The Quran into Polish (and Belarussian) which dates back as far as the 16th century. This translation is known as a Muslim Tafsir.