The impacts of chemical treatment and modified atmosphere on enzymatic changes in minimally processed apples were evaluated. Slices of apple cultivars Golden Delicious and Red Delicious were packed in plastic bags with modified atmospheres: 85% N₂, 5% O₂, 10% CO₂ (MA) and 78% N₂, 21% O₂, 1% other gases (NA). The changes in colour, firmness, polyphenoloxidase activity, total phenols content and concentration of single phenols during storage were measured. It has been found that the effects of storage atmosphere and antioxidant treatment were not as important as the choice of apple cultivar. Red Delicious is a cultivar with high concentration of phenolic compounds and high activity of polyphenoloxidase; therefore it is difficult to limit the very fast enzymatic changes and subsequent discoloration.