This paper will deal with the issue of deaccession of museum materials from the collection, using the example of the restitution of those collected during the period of Nazism and World War II. At the beginning, an introductory speech will be given on the management of museum collections, defining deaccession as one of the main management activities, recalling the rules and methods of deaccession and the behavior when removing museum material from the collection. Then, using specific examples related to the period of Nazism and the Second World War, an attempt will be made to explain the restitution process of materials that were stolen from their original owners by the Nazis and ended up in museum institutions. The focus will be on the Gurlitt collection, whose owner Cornelius Gurlitt had about 1,500 works in his possession, a few of which were proven to have been acquired illegally during the war, and on the case of the theft of Gustav Klimt’s works owned by Ferninand Bloch-Bauer, as well as the project of the British Museums Association, the purpose of which was to investigate whether some of the illegally acquired objects are in the holdings of British museums and galleries and to prepare them for possible deaccession. The case of rescuing works of Serbian provenance from the area of Fruška gora etc. will also be mentioned, which was dealt with by our renowned museum curator Vladimir Tkalčić in the framework of his activities during the Second World War at the Museum of Arts and Crafts in Zagreb.