The aim of this study is to investigate the usability and usefulness of interactive tabletop technologies to support group creativity. We implemented a tabletop interface enabling groups of 4 participants to build mind-maps (a tool for associative thinking). With 24 users in a within-group design, we compared its use to traditional paper-and-pencil mind-mapping sessions. The results showed no difference in idea production, but the tabletop condition significantly improved both subjective and collaborative dimensions, especially by leading to better-balanced contributions from the group members.