The Law of the 13th of July, 1939 on Abolishing Fees Tail did not abolish itself that institution, represented then by 55 estates subject to different regulations in divers parts of the territory of the Republic of Poland, but it provided for an evolutive process of abolition, to be initiated by the patriarch or ex officio, and accomplished by the decision of the Appellate Court on abolition. Abolition meant that the patriarch, having been a “possessor” of the fee tail belonging to the whole family, was to become a regular owner of its goods. Because of the World War, II no fee tail was abolished within the framework of that Law. All existing fees tail were abolished ex lege, in the new post-war conditions marked, in particular, by realization of the land reform, by the 1946 Law-Decree providing for introductory provisions of the succession law. It repealed the 1939 Law, but maintained in force its substantive provisions defining the essence of fees tail. In the article, an analysis is developed of legal problems related to legislation on abolition of fees tail that arise out in the present Polish legal practice. It relates to the problem of the right of the 1939 fee tail patriarch to receive, on the basis of the 2005 particular law, a compensation for estates left on the pre-war territory of the Republic of Poland taken by the USSR; it could be given only to the then owners being physical persons, and not to simple holders. There have been two cases decided over by administrative courts, and their approach, and to a certain extent decisions, have been quite different. The other problem examined relates to the present right of ownership of library collections having belonged to two fees tail, and the respective rights of the National Library of Poland that keeps those collections.