The active layer thickness, CO2 emission, and contents of organic substances (including the total organic carbon, labile carbon, and the carbon of microbial biomass) in the soils of flat-topped peat mounds in the area of the Nadym Experimental Station in the north of Western Siberia (experimental site CALM R1) are characterized by considerable spatial variability. The low values of the CО emission are confined to the microelevations on the peatland surface. The high values of the emission (>200 mg CO/(m h)) are typical of the soils with the highest content of the carbon of microbial biomass and the lowest content of the labile organic carbon. The soils of elevated flat-topped peat mounds statistically differ from the soils of waterlogged mires in the contents of total, labile, and microbial carbon and in the CO emission values. Though the soils of elevated flat-topped peat mounds are characterized by the high content of the carbon of microbial biomass (4260 ± 880 mg С/kg soil), the CO emission from them is low (158 ± 23 mg CO/(m h)), which is explained by the structure of microbial communities in the cryogenic soils and by the effect of specific hydrothermic conditions. [ABSTRACT FROM AUTHOR]