ENIn the Library of the Lithuanian Academy of Sciences there are over 33 private collections of well-known scientists, publicists and literary men of Vilno and beyond, whose inventory registry covers the modern era. They were not thoroughly analyzed Ьу historians studying the time period under discussion, despite the fact they sometimes include original documents concerning the period from the 16th to the 18th century. The following article is barely an outline of the issues that await our scientific research. Eight collections located in the mentioned library will be analyzed. Most documents that I have encountered in these private collections concern the financial matters of different Lithuanian families. Most often they are extracts from estate and city land records, and also from the Chief Tribunal of Vilno. For the most part, they are copies issued by appropriate offices of the Grand Duchy of Lithuania for use in court cases. There can also be found sporadic instances of handwritten correspondence, but these also deal with matters relating to landed estates, or to dispositions issued to the administrators of estates. The discussed documents are often the only ones concerning particular matters and families that survived to our times; thus, they are of great value for researchers studying the lineage or fortunes of specific gentry clans.