Abstract. Current brain-computer interfacing (BCI) research focuses on detection performance, speed, and bit rates. However, this is only a small part of what is important to the user. From human-computer interaction (HCI) research, we can apply the paradigms of user-centered design and evaluation, to improve the usability and user experience. Involving the users in the design process may also help in moving beyond the limited mental tasks that are currently common in BCI systems. To illustrate the usefulness of these methods to BCI, we involved potential users in the design process of a BCI system, resulting in three new mental tasks. The experience of using these mental tasks was then evaluated within a prototype BCI system using a commercial online role-playing game. Results indicate that user preference for certain mental tasks is primarily based on the recognition of brain activity by the system, and secondly on the ease of executing the task.