Comment lines in the software source code include descriptions of codes, usage of codes, copyrights, unused codes, comments, and so on. From the viewpoint of fault-prone module prediction, comment lines may have useful information for faulty modules as well as in code lines. In fault-proneness filtering approach, which we have been proposed based on text filtering technique, comment lines and code lines in a source code modules are regarded as text without any distinction. For better prediction results of fault-prone modules, the effects of the comment lines on prediction should be investigated. This study conducts experiments using Eclipse data sets to reveal the effects of comment lines on the fault-proneness filtering. The result of experiments was somehow unexpected: pre- diction using comment lines shows better recall and precision than that of code lines.