Personas are results from user studies and viewed as a design and a communication tool in user-centered design processes. There were many studies addressing how to create good personas but what types of personas and how personas could help in ideation processes were less discussed in past works. In this paper, we conducted a comparative study to explore effects of personas on the ideation process and idea qualities in a brainstorming setting. The results indicated that personas could enhance the ideation process and design deliverables on two aspects: personas could help both individual designer and a group of designers focus on the target user group during the ideation process; and the delivered ideas or concepts were viewed more relevant to the user groups and were more comprehensive.