We assessed the effect of eight Japonica rice (Oryza sativa L.) cultivars on CH4 emission in typical mono-rice paddy soil based on our hypothesis that the CH4 flux may differ significantly among rice cultivars because each rice cultivar has different physiological and anatomical characteristics and may differently affect the microbial abundance involved in the CH4 dynamics in paddy soil. The rice cultivation experiment was conducted over 3 years (2010-2012) at the Duryang Experimental Station, Gyeongsang National University, Sacheon, South Korea. Eight cultivars selected included the late-maturing (135 days) such as Chuchung, Dongjin, Ilmi, Junam, Nampyeong, Samkwang, and early-maturing like Odae and Woonkwang cultivars. A closed chamber method (Ali et al., 2009) was used to estimate CH4 fluxes for the entire cropping periods. For determining CH4 production potentials, methanogens abundance and activity, total carbohydrates and dissolved organic C in soil and organic acids in solution solutions were analyzed. Methanotrophs abundance and activity in soil, dissolved CH4 and CO2 in soil solution as well as root oxidation area were investigated by rhizobox and digital image analysis experiment for characterizing CH4 consumption capacity. The overall patterns of CH4 emission rates were similar among the cultivars for each year. A typical CH4 emission pattern was observed, in which, CH4 emission rates were lower at the initial vegetative stage, rapidly increased with the developing anaerobic soil condition and plant growth, and peaked at the maximum heading stage of the rice plant. The CH4 emissions then rapidly returned to background levels at harvesting stage. The mean CH4 emission rates (0.15-0.37 g m-2day-1) and total CH4 fluxes (20.0-50.0 g m-2) varied significantly among the cultivars (P<0.05). Methane fluxes were directly affected by the substrate-producing potential and gas transport capacity of each cultivar rather than the external plant growth variables. With regards to CH4 production, methanogen abundances, carbohydrates and dissolved organic C in soil and total organic acids in soil solution differed significantly among the cultivars. While with regards to CH4 consumption, dissolved[CH4] and [CO2] in soil solution as well as root oxidation area differed significantly among cultivars. Methane fluxes were highly positively correlated with methanogen abundances, soil carbohydrates and dissolved organic Cs, and total organic acids in soil solutions while negatively correlated with methanotrophs abundance in soil, [CO2]-C/ [CO2 + CH4]-C in soil solution and root oxidized area, but not with any of the apparent plant growth parameters. Rice cultivar and growth stage did not have an influence on the community structures of methanogens and methanotrophs. In conclusion, the selection and development of a cultivar with lower CH4 flux may be an effective countermeasure for decreasing CH4 emissions from rice paddy soil.