The transport and photochemical transformation of tropospheric ozone and carbon monoxide in East Asia was studied by using a three-dimensional global atmospheric chemistry transport model MOZART-2 with two different emission scenarios. The simulated mixing ratios of ozone and carbon monoxide are compared with ground level observations at Minamitorishima and Ryori in Japan and it is found that the model reproduces the observed features reasonably well. Minamitorishima, located about 2000 km southeast of Tokyo, is surrounded by ocean, while Ryori is located north of 30ºN, belonging to the East Asia monsoon area and being greatly affected by continental outflow. Due to differences in geographical locations and meteorological factors as mentioned above, the changes in emissions significantly influence the mixing ratios of ozone and carbon monoxide over Ryori.