The paper discusses the method of determination of the methane content in the atmosphere from spectra of AIRS sensor installed aboard AQUA satellite and the method testing with data of 2005-2006. Maps of the horizontal methane distribution and seasonal variations of CH4 in the atmosphere over wetland of Western Siberia are presented. Sets of clear sky AIRS spectral data selected for the period from spring of 2005 to fall of 2006 and direct/inverse FIRE-ARMS model were used. The methane content in the atmospheric column was determined, and seasonal maps of the horizontal methane distribution in the atmosphere of Western Siberia (58-67°N; 58-90°E) were constructed. Seasonal mean methane variations in the atmosphere of the studied region were revealed.