Based on the analysis of Zbigniew Oleśnicki's attitude towards the Polish-Lithuanian union in the years 1434-1453, the author comes to the conclusion that the bishop of Krakow consistently sought to continue the policy developed during the reign of Władysław Jagiełło. Its basis was the belief that the Polish Crown must maintain the union with Lithuania at all costs, while avoiding armed conflict. Particular efforts were made to implement this policy in the Polish Crown in the years 1440-1447, taking into account the fate of the union. Out of concern for the fate of the union, Oleśnicki contributed to the election of Casimir IV as king of Poland. The aim was to rule both countries by one ruler. The failure to establish a separate Grand Duke of Lithuania had a double meaning: it contained Lithuanian separatism and prevented territorial disputes. Oleśnicki's hope that Kazimierz would care about Lithuanian policy like his father did not come true. The young king, bound by an oath to the Lithuanians, had to represent the Lithuanian position at least temporarily. He soon began to think in dynastic terms, which, however, did not refer to Jagiełło's policy. The author also states that opinions about Oleśnicki's incorporationism are a pure invention of historiography. His attitude towards the union can be reduced to the following points: a) insistence on maintaining the legal subordination of the Grand Duchy of Lithuania to the Polish Crown; b) demand that the king prohibit Lithuania from pursuing a foreign policy contrary to the interests of the Polish Crown; c) opposition to the violation of the established territorial status quo. It is worth noting that Oleśnicki did not stubbornly stick to his views, but was able to adapt them to current politics. Like other dignitaries of the Polish Crown, however, he could not accept territorial concessions to the Grand Duchy, which could deprive the Polish Crown of its legal domination over Lithuania.