The bryophyte flora of two northern Kuril islands, Paramushir and Shumshu, is studied. The compiled list includes 97 species and 4 varieties of liverworts and 154 species and 1 variety of mosses. The flora is characterized with the considerable proportion of East-Asian species. There is a great difference between these two islands in species composition: Shumshu is characterized with a great number of heliophytes, while Paramushir – with mountain species, mainly epilithic ones. Contemporary volcanic activity considerably affects the flora of Paramushir Island, primarily, due to occasional ashfalls resulting in destruction and degradation of a some of plant communities, as well as in supplying unoccupied substrates.