A relatively high-resolution (T106) atmospheric general circulation model (AGCM) was used to simulate the present-day climate with two different assumptions in cumulus parameterization. While the two runs show comparable performance for the annual mean precipitation, one shows much better agreement with satellite-based analysis data for the extreme daily precipitation than the other. Accumulation of convectively available potential energy is shown to be important for more realistic intensities of extreme precipitation. This demonstrates that the performance of an AGCM for extreme precipitation is strongly dependent on cumulus parameterization even when the resolution of the model is as high as 1°, but can be reasonably good with an adequate choice of cumulus parameterization. A time-slice doubled CO2 experiment was also conducted with the better version of the model. Though the global mean percentage change is larger for extreme precipitation than for the annual mean, this relation is found to vary regionally.