The article deals with the activities of the Ukrainian Insurgent Army (UPA) in the western part of Lemkivshchyna (Łemkowszczyzna) in 1945–1948. This issue has not been researched into by the historians very often as it is considered a third-rate activities of UPA. Jasło district in 1946–1947 was covered by the activities of the troops (sotnia) of Roman Hrobelski codename ‘Brodycz’ from the battalion (kurenia) of Martyn vel Wasyl Mizerny ‘Ren’ and the independent subunit of Michał Fedak ‘Smyrny’. The number of soldiers in those units ranged from 100 to 150. In 1945 in the Jasło district there were only singular operations organized by the Ukrainian nationalist underground including the attack on Krempna. The period of the most intense activities of UPA in the discussed period was the second half of 1946. The main motive of the UPA offensive operations was the need to get food, clothes, and to a lesser extent pursue propaganda and ideological goals, that is to say infl uence the local society of Lemkivshchyna which in majority was not pro-Ukrainian, and often loyally co-operated with the security apparatus and the people’s authorities. Starting with the beginning of 1947 the attacks of the UPA troops were rarer and rarer, despite the fact that in the fi rst months of that year the presence of UPA soldiers was noticed in several villages of the Jasło district. The following factors infl uenced the decline in UPA activities: the increase in the military efforts of the Polish Army, which co-operated with the Citizens’ Militia, the Volunteer Reserves of the Citizens’ Militia and the Offi ce of Public Security as well as the change of tactics of fi ghts with irregular Ukrainian units. In the course of the Vistula River (‘Wisła’) operation the UPA troops were not able to slow down the displacement operation. At that time solely small or dispersed UPA units resorted to petty thieving operations. In July 1947 the commander of the last unit (sotnia) operating in Jasło district received an order to evacuate to the American occupation zone in Austria. In Jasło district the Polish-Ukrainian confl ict differed from the fights with UPA waged in the areas located in the more remote eastern parts of Poland. There were no larger clashes with UPA troops there, and a small number of casualties on both sides of the confl ict are known. As a result of the operations of the Ukrainian underground the material losses were incurred by the villages located in the southern part of Jasło district – as they were partially burnt down.