Some studies on technology-supported peer feedback in the writing classroom claim that it reduces the threatening atmosphere caused by face-to-face interaction and that the discourse patterns and language use in the electronic feedback are more flexible than in spoken discourse. Others present a negative view that the comments generated from technology-supported interaction tend to be superficial and that technical problems reduce participant motivation in peer interaction. These contradictory results call for a systematic literature review of this topic. An exhaustive literature search in a variety of academic sources identified 95 studies from 1990 to 2010 dealing with peer feedback in English as a second or foreign language (ESL/EFL) writing classrooms. Of these, 54 contained qualitative data, 20 of which were specifically on computer-mediated peer feedback. Concentrating on these 20 articles, the researcher conducted comparative reviews of the characteristics, the pros and cons, and the differences between synchronous and asynchronous interaction for this mode of peer feedback, using Glaser and Strauss' Grounded Theory (1967) constant comparison method. Based on the findings, several main themes are identified and three implications involving pedagogy, group dynamics, and training for future research on this mode of peer feedback are discussed.