A lot of supporting tools for vitalizing brainstorming sessions have been proposed. Some of them show the participants hints for discussions, e.g. keywords and images, to the members. The author’s research group also has proposed a supporting system for vitalizing brainstorming sessions, in which related images of ideas thrown in the session are shown for the participants as hits. However, the effects of this type of hint had not been investigated yet. Thus, experiments were conducted to show the effects. In the experiments, effects of three types of hints, (1) relevant words of the words used in ideas presented in the discussion, (2) images retrieved by using words used in ideas presented in the discussion as keywords, and (3) images retrieved by using relevant words of the words used in ideas presented in the discussion as keywords, were compared. As a result, it became clear that the third type of hints can increase number of utterances and diversity of the subjects in discussions.