This paper reports an investigation of the impact of students cognitive style on their effective use of educational text-based computer-mediated conferences. The research centres on an empirical study involving students from three courses run by the British Open University. Statistical analysis of the data does not suggest that cognitive style has a strong influence on student participation in the conference, but does suggest that, contrary to expectations, imagers may send more messages to conferences than verbalisers. The data also suggest a possible link between certain cognitive styles and course completion, and that the interaction of different styles within a group, as described by Riding and Rayner's (1998) team roles, may have an indirect influence on task completion.