The cottid genus Radulinopsis Soldatov and Lindberg is recognized as a valid taxon including two species, R. derjavini Soldatov and Lindberg and R. taranetzi sp. nov., both distributed in shallow waters around Hokkaido, Japan, and the Russian Far East. Radulinopsis taranetzi differs from R. derjavini in having an almost naked body, teeth on the prevomer, and higher meristic counts. Radulinopsis derjugini Soldatov is synonymized with R. derjavini. A key to species of Radulinopsis and related genera is given. Based on a cladistic analysis of 18 morphological characters, Radulinopsis is the sister group of the Japanese genus Astrocottus, and the monophyletic eastern North Pacific group comprising Radulinus plus Asemichthys is the sister group of the western North Pacific group of Radulinopsis plus Astrocottus. Triglops, having a wide distribution throughout the North Pacific and North Atlantic, is putatively the sister group of a monophyletic group including these four genera. Bolin's genus Radulinus (including Radulinopsis as a subgenus) and Taranetz's subfamily Radulinae (including only Radulinus and Radulinopsis) are polyphyletic and therefore invalid.