In the literature, there has been a focus on the effectiveness of larger sized electronic brainstorming groups; however, mechanisms for its effectiveness still remain open to question and some methodological concerns (e.g., the evaluation of ideas and the typing speed, and the use of different formats) continue to be important problems. To overcome such problems, a series of experiments were conducted. All subjects were exposed to the two-minute typing speed test which was overlooked in the previous studies in electronic brainstorming. In the first experiment the effect of the group size (4, 6, and 8 person groups); in the 2nd experiment that of group size (4, 6, 8, 10, and 12 person groups) with the memory instruction, and in the 3rd experiment that of group size (4 and 10 person groups) with two lengths of brainstorming session (15 and 25 minutes) were investigated on the brainstorming performance. Results showed that unique and original ideas increased as the group size increased. However, the group size did not affect the performance of one individual within these groups. Memory instruction inhibited performance in the shorter session (15 minutes) of brainstorming but enhanced it in the longer session (25 minutes) of brainstorming. Typing speed affected the total number and unique ideas but not the originality and feasibility of these ideas. In conclusion, these findings demonstrated that group size enhanced creative ideas (unique, original, and feasible ideas). Consistent with the literature, the beneficial effect of memory instruction could be evident in the longer session of brainstorming rather than the shorter one. These findings were discussed in light of the relevant brainstorming literature and their implications on educational, health and organizational settings.