ENThe beginning of the common Polish-Lithuanian state was in 1385 when a personal union was concluded in Krewo, and the end was in 1795 when Russia, Prussia, and Austria realized the Third Partition of Poland. In the years 1385–1569, the Kingdom of Poland and the Grand Duchy were united by a personal union, which meant that each Grand Duke of Lithuania was elected as king of Poland. The Union of Lublin, concluded in 1569, introduced a real union with a common ruler, the Sejm, and foreign policy. However, a number of differences were maintained in offices, administration, army, fiscal and judicial law in both parts of the state. The constitution, adopted on May 3, 1791, did not mention the Polish-Lithuanian union, but the laws passed to clarify and to implement it defined new rules of the Polish-Lithuanian union. Keywords: The Constitution of 3 May, The Polish-Lithuanian Commonwealth, Polish-Lithuanian relations, The Reciprocal Guarantee of Two Nations. [From the publication]