The effect of drainage and long-term agricultural use of peat soils in the Rostov Lowland (Yaroslavl oblast) on the actual and potential emissions of carbon dioxide, methane, and nitrous oxide is determined. The sorption of methane and nitrous oxide is studied. Emissions of greenhouse gases from peat soils of different degrees of cultivation are estimated. The highest methane emission is revealed in the uncultivated peat soil (the control variant). The maximum rate of organic matter mineralization as estimated by the intensity of the carbon dioxide emission is seen in the agrogenic peat soil cultivated for 30 years. The maximum denitrification activity is revealed in the buried cultivated peat soil. The main product of the denitrification processes in all the studied soils is represented by molecular nitrogen.