The copper ore deposit of LGOM (Legnica-Glogow Copper Basin) is located in the Foresudetic Monocline (SW Poland) and has a polymetallic character because of content of silver, lead, copper and accompanying metals such as cobalt, zinc, nickel, rhenium and gold. Over 110 metalliferous min- erals were identified in the deposit. A sedimentary nature of the deposit results in necessity of fine grinding for effective liberation of sulfide particles prior to flotation. Fine dissemination of metalli- ferous minerals, particularly in the carbonate type ore, considerably reduces the susceptibility to ef- fective liberation. A beneficial effect of non-oxidative leaching of carbonate gangue with sulfuric acid on copper ore flotation was presented in the paper. It was shown that the non-oxidative leaching of the flotation feed is a selective process leading to liberation of sulfide minerals disseminated in the gangue carbonate matrix. Acid leaching causes chemical decomposition of carbonate matter and re- leases fine grains of copper minerals. Kinetics of leaching of the investigated ore sample with various amounts of sulfuric acid were presented. It was shown that after decomposition of 70% of carbonates in the flotation feed, metal recovery and concentrate grade increased remarkable in comparison to the results observed for the unleached feed. The products of leaching contain solid hydrated calcium sul- fate (gypsum), soluble magnesium sulfate and gaseous carbon dioxide. Carbon dioxide evolving dur- ing the reaction creates a non-oxidizing atmosphere in the pulp during leaching and therefore effec- tively prevents digestion of metals from sulfide minerals. The liberation of copper minerals due to leaching provides better separation of metallic ore components by flotation.