The earth warming is now one of the most serious environmental problems. Of all the greenhouse gases, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are deeply related to agriculture. Methane is emitted from paddy fields, and nitrous oxide from upland fields according to fertilizer application, respectively. As is well known, paddy fields are one of the most important sources of methane fluxes. Hitherto, studies on methane fluxes from paddy fields have mainly focused on their quantitative estimation, while production and movement of methane in paddy soils have not been major concern among researchers. Paddy soils are microbially dynamic environment, in which carbon dioxide and methane are produced and emitted through various processes. In this paper, the processes involved in the production and movement of carbon dioxide and methane in paddy soils were reviewed with special consideration to chemical properties of these two gases and the role of percolation water on their fates in paddy soils.