This article discusses our work examining asynchronous eTutoring comments and how we determined whether tutor comments on papers submitted to our writing center were effective. Drawing from the fields of writing center theory, education, and rhetoric and composition, we define effectiveness as a combination of revision and improvement factors (Faigley and Witte; Stay; Bowden). Data collected consisted of initial and subsequent drafts of student papers submitted for eTutoring sessions, including the comments a tutor made on each paper. We categorized the comments and corresponding revisions to answer the following questions: which types of comments result in the greatest number of revision changes? And, do those comments, according to our definition, align with the types of comments we find to be the most effective? We found that frequency and effectiveness were not the only factors in determining a comment’s importance. We emphasize the necessity of instruction and scaffolding in tutor comments to potentially increase their effectiveness and student understanding.