The diet composition of brown bear (Ursus arctos) and Asiatic black bear (U. thibetanus) studied in the Sikhote-Alin Biosphere Reserve and its surroundings in 1999–2014. We defined the content of 658 scats of two bear species. The percentage overlap of brown bear and Asiatic black bear diet was 81,1 %, indicating a significant similarity between them. The basis of the diet of both bear species are food of vegetable origin: in the fall – Korean pine (Pinus koraiensis) nuts and acorns of Mongolian oak (Quercus mongolica), in the summer – herbaceous vegetation. Food of animal origin more important in the diet of brown bears in comparison with the Asiatic black bears (occurrence in scars 21,6 and 5,9 %, respectively). Mammals in the diet of the bears play the greatest role in the spring. The competition between the two bear species exacerbated by a shortage of food resources, especially in the years of bad harvest of nuts and acorns.