We mobilize theories of Corporate Governance and the theory of the social psychology of decisionmaking small groups to understand the operational process of the public hospital supervisory board
(SUB). More precisely, we empirically test the mediation relationship of the decision-making process
(effort norms, use of knowledge and skills, and conflictcognitive) between its structure (size, thecomposition, and diversity) and the performance of its roles (strategy, control, and service). 320questionnaires coming from members of the French public hospital supervisory board werecollected. The aggregation of these individual answers generates a sample of 159 public hospitalsupervisory boards. The results of the tests of the assumptions of the research model confirm thefact that the structure of the SUB does not influence the performance of its roles. However, SUBeffort norms affect positively the performance of its roles positively. Only effort norms and the useof knowledge and the skills partially play the role of mediator between the SUB structure and the
performance of its roles. Practical and theoretical implications are exposed in the discussion.