The aim of this study was to compare nitrous oxide (N2O) emissions using the IPCC methods - first (Tier 1) and third level (Tier 3). Simulation on third level was performed using a Denitrification-Decomposition (DNDC) model. The simulations showed that based on the Tier 1 methodology average N2O emissions for Poland were 3.51 kg N/ha, whereas for the DNDC model - 1.86 kg N/ha. According to the DNDC model simulated N2O emissions for the entire territory of the Poland constitute 54% of the emissions calculated according to Tier 1 method. The obtained results indicate that the use of biogeochemical model which takes into account environmental conditions allow for accurate estimations of N2O emissions when drawing up reports in accordance with the commitments on reporting greenhouse gas (GHG) emissions.