Spatial relationships of “small” species from the group Sicista betulina in the territory of Eastern Europe are investigated. It is shown, that species have ranges of distribution which are not overlapped. New findings support continuous range of S. strandi from East-Russian Highland to Northern Caucasus, and border between two species pass through watershed of the Oka basin and the Don basin. Correspondence of parapatry to lower level of ecomorphological differentiation of species is shown: Hutchinsonian ratio for craniometrical characters of allospecies reach just 1,03 (with maximum 1,13). For exterior characters, HR in sympatric pairs reach value 1,37. As a whole, wide sympatry among “small” species of Sicista occurs just in cytogenetically most different forms, that close the loop strandi–betulina–subtilis–severtzovi. All the data confirm a concordance of biogeographical, ecomorphological and cytogenetical levels of differentiation in studied mammal group.