Oil and gas is a key sector for greenhouse gas inventory of the Russian Federation represented by non-CO2 greenhouse gases methane (CH4) and nitrous oxide (N2O). The CH4 and N2O emission estimates are mainly performed with the use of default method (IPCC 2000). As a result of continuous inventory improvement, the national parameters for oil and gas sector were derived and IPCC methodology was adjusted. The parameters were developed on the basis of specific features of producing industry and the properties of oil and gas produced. These developments enabled a shift to tier 2 estimation approach (IPCC 2006). The aim of the study was to highlight the differences between both estimation methods. For this purpose, the CH4 and N2O emissions were estimated from 1990 to 2009 with the use of default (tier 1) and a combination of tier 1 and tier 2 methods. The results of the estimates were compared and their uncertainty assessed. The results of comparison showed insignificant differences in the emission profile. Th...