In this paper, we propose an efficient method for extracting scene tags from online video annotation (e.g., comments about video scenes). To evaluate this method by applying extracted information to video scene retrieval, we have developed a video scene retrieval system based on scene tags (i.e., tags associated with video scenes). We have also developed a tag selection system that enables online users to select appropriate scene tags from data created automatically from online video annotation. Furthermore, we performed experiments on tag selection and video scene retrieval. We found that scene tags extracted by using our tag selection system had better cost performance than ones created using a conventional client-side video annotation tool.