Cancer support groups are an important source of support for cancer patients, yet little is known about the characteristics of, and barriers to, effective leadership, and the training needs of both professionally trained and untrained leaders. This study explored the views of 179 leaders of 184 cancer support groups in NSW, Australia, regarding these issues. Four hundred and sixteen members of 50 groups selected from the larger cohort completed questionnaires eliciting the importance of group processes, including leader qualities, and satisfaction with group leadership. Finally, members of nine groups participated in focus groups regarding effective group processes. The importance of the leader(s) was emphasized in all stages of the research. Fifty-nine percent of group leaders were currently experiencing a difficulty, primarily related to infrastructure or group process. Three characteristics of effective leaders were identified: educational qualities, facilitation skills, and personal qualities. There is clearly a need to develop and evaluate effective interventions to maintain leaders in these roles, if the proven benefits for cancer patients are to be protected.