Abstract: Palsas and peat plateaus have an important role in the bio- and geodiversity of Northern environments. The peat of the palsa is an archive of geochemical and biochemical conditions of high quality. The palsa peat bog of Eletsky was studied in the north-east of the Bolshezemelskaya tundra (67°16′ N, 63°39′ E). Palsa of 1.5 to 4 m height were studied in detail. The content of carbon and nitrogen in the peat has been determined, as well as the isotopic composition of carbon. The analysis of the carbon and nitrogen content in plants growing both on the surface of the heave mounds and in the depressions between the mounds was carried out. Variations in C/N values indicate changes in the peat moor humidification regime and the rate of peat decomposition. The results obtained indicate a high degree of watering of the Eletsky massif as a whole during the accumulation of peat and mainly anaerobic conditions of its decomposition. It was found that the change of plant associations also affected the value of C/N. Studies of the Eletsky palsa peat bog have shown that the isotopic composition of carbon is determined primarily by the botanical composition of plant remains. New ecological niches are formed in the process of palsa growth, some plant communities are replaced by others. There was not detected difference of the isotopic composition of thawed and frozen peat.