This study aims to examine the effects of the online writing experiences of English as a foreign language (EFL) learners on their self-efficacy, attitudes, and performance in a computer-mediated writing classroom (CMC). Although the close relationship between students' computer experiences and class performance has been positively confirmed in many studies, it has rarely been examined in the context of an EFL writing course. In this study, two groups of Korean university EFL learners, regular (15) and non-regular (17) online writers, were compared regarding their self-efficacy, attitudes, and the extent to which they incorporated online peer feedback into revision. The results reveal that regular online writers, in comparison with non-regular online ones, are likely to have more positive attitudes towards CMC and to incorporate feedback into revision more successfully and extensively. This finding implies that the introduction of a new technology should be accompanied with extra assistance and device to those who are not familiar with the technology.