The effect of mulching on the size of berries of three highbush blueberry cultivars (Bluecrop, Northland, Spartan) cultivated on mineral soil in 1997–2000 was estimated. Three organic materials: pine bark, peat and sawdust, were used in the experiment. Weight of 100 fruits and their diameter were measured in each harvest. Soil mulching did not have influence on the size of blueberry fruit.