The character of distribution of two species from the genus Ixodes, the Taiga tick Ixodes persulcatus and Ixodes pavlovskyi in the plain part of Western Siberia is analyzed. The northern border of the range of I. persulcatus in HMAO-Ugra was clarified on the basis of long-term data on the population density of adult and immature ticks (1960-2011). The shift of the southern border of the species range in Western Siberia at the background of anthropogenic transformation (forest restoring activity, stopped sanitary forest cutting, road construction etc) is demonstrated; peculiarities of the distribution of the Taiga tick in some localities of the southwestern Siberia is analyzed. The modern state of the tick population in the joint dwelling zone of I. persulcatus and I. pavlovskyi is characterized. Possible reasons of changes in the structure of tick communities toward total prevalence of I. pavlovskyi in recreation zones of Novosibirsk and Tomsk are discussed. It is noted that the most significant changes in the character of distribution of these two tick species in Western Siberia had evidently occurred after 1990. Just in this period, local stable populations of the Taiga tick to the south of its main range in Western Siberia (within Omsk and Novosibirsk Provinces) were formed; the character of its distribution in the right bank of the Ob River (Novosibirsk Province) and in the valley of the Tom River (Tomsk Province) had changed; I. pavlovskyi became the dominating species.