The study of the word-formation level of the Russian dialect language is mostly represented by the analysis of the word-formation types of concrete-noun derivatives. Study of derivatives with the suffix -ush/a offers unique insights into derivational niches, due to the ambiguity of the motivating basis and the polyvalence of the suffix. The description of the territorial distribution of derivatives with the suffix -ush/a in Western Russian dialects of the European part of Russia and in Siberian dialects demonstrates the specifics of their functioning: Western dialects have a large number of archaic models, and Siberian dialects indicate the shift of models towards personal nominations, often with negative connotation; at the same time, the stability and unity of elements of word-formation niche may indicate a relatively new linguistic trend, which characterizes Siberian dialects.