Institutions help solving collective action problems and common-pool resources need institutions for their successful and sustainable management. However, institutional creation, functioning and changing are also second level collective action problems with no automatic solutions. This paper analyzes institutions functioning and change in users-managed irrigation systems in Valle d'Aosta, a northern Italy alpine region. Irrigation systems represent a complex resource, crucial for the traditional economy of the valley. Although the transition to advanced economy has partially reduced their importance, most of them are still in use and managed by the farmers themselves, with only external help from the region's administration. Nine cases are here studied, and a special focus is directed toward the social elements affecting both agricultural and institutional performance.