The purpose of this current study aims to examine how much Korean EFL students incorporate their given peer responses into their final versions of writing in two different types of CMC environment, chatting and bulletin board, and whether there was any improvement in participants’ writing quality in the final drafts. 38 Korean EFL participants wrote first drafts, received peers’ responses through either chatting or bulletin board, individually revised their drafts based on their peer responses and wrote their final drafts. The overall results revealed that regardless of using either chatting or bulletin board, the participants incorporated higher portion of their given responses into the revised drafts. Although no significant differences were obtained with respect to two different modes, chatting and bulletin board, in terms of writing improvement in participants’ final drafts, there were significant differences found within chatting and bulletin board classes with both holistic and analytic measurement. Therefore, the present study suggests the importance of utilizing both CMC tools in writing environment for EFL students and applying them at appropriate steps in the writing process.