Diversity and distribution of species of the wood-decaying genus Armillaria were investigated in the Uholsko-Shyrokoluzhanskyi protected forest massif of the Carpathian Biosphere Reserve. Armillaria gallica (Marxmüller & Romagnesi), A. cepistipes (Velenovsky), A. ostoyae (Romagnesi) Herink and Armillaria mellea (Vahl:Fr.) Kummer were identified for the first time in Transcarpathian Ukraine. Rhizomorphs of A. cepistipes and A. gallica were very frequent both in the soil and on the root collars of trees and their abundance decreased with increasing altitude of the plots. Species composition indicates that in the investigated forests the genus Armillaria plays an important role as wood decomposer.