The rate of dead fallen wood decomposition varies across the sections of trunk and the tree species: most rapid decomposition occurs in the upper part of the trunk (the loss of basic density on average is 4.4 % for spruce and 2.0 % for fir per year), most slowly — in the bottom parts (2.7 % and 0.4 % respectively). The rate of coarse woody debris (CWD) decomposition did not depend from the influence of industrial pollution. The share of spruce CWD, inhabited by wood-destroying fungi, was significantly higher (р<0.01) in background area as compared to polluted one; the share of fir CWD did not differ significantly among the areas of investigation.