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.