A new polypore, Aporpium macroporum Niemelä, Spirin & Miettinen, is described on the basis of material from Finland, Poland (Białowieza National Park; type locality), European Russia, Belarus, Estonia, and Latvia. It grows primarily on fallen aspen trees and prefers old forests with abundant coarse woody debris. Aporpium caryae is an American taxon, and its European kin is A. canescens; A. macroporum differs from them in having wider pores, softer consistency, and paler colours. The spores of the new species are wider than in A. canescens, and longer than in A. caryae. The three species can be distinguished by their ribosomal DNA ITS sequences. We briefly discuss the heterobasidioid genera Aporpium, Elmerina and Protomerulius.