Additions to the second edition of the Catalogue of the Lepidoptera of Russia are given in the present communication. They concern three East Siberian regions of the Russian Federation: Irkutsk Province, the Republic of Buryatia, and Zabaikalskii Territory. An annotated check-list includes 54 species of 6 families. The publications with records of these species from the area studied are cited. For Irkutsk Province, 20 species are listed, 16 of which are recorded for the first time. For the Republic of Buryatia, 35 species are given, 19 of which are recorded for the first time. For Zabaikalskii Territory, 10 species not recorded previously are reported. Eupithecia impolita Vojnits, 1980 is new to the Russian fauna. The distribution limits are expanded for 9 species: the new eastern limit of the distribution is established for 3 species of Noctuidae: Photedes captiuncula (Treitschke, 1825), Photedes fluxa (Hübner, 1809), and Noctua interposita (Hübner, 1790); the western border of the distribution range is shifted for Eogystia sibirica (Alphéraky, 1895), Scopula agutsaensis Vasilenko, 1997, Paragona multisignata (Christoph, 1881), Arytrura subfalcata (Ménétriés, 1859), Acronicta hercules R. Felder et Rogenhofer, 1874, and Sympistis kaszabi (Ronkay, 1988).