Among the various analytical dimensions purporting to an appraisal of the replication potential of eParticipation projects, institutional factors deserve considerably more attention by theorists and practitioners alike. This paper introduces a "process oriented" definition of sustainable eParticipation, based on five key attributes: juridical compliance, legitimacy, social value, efficiency, and productivity. These can be used to assess the level of potential integration of a participatory practice or trial within the legal, political, social and organisational contexts of the public sector institutions involved. We posit that sustainable participation will emerge whenever these five dimensions are not jeopardised, compromised, or are left unaltered, by the introduction of participatory elements into any decision-making process regarding issues of public relevance. Empirical investigation is recommended to assess the impact of specific Preparatory Actions on eParticipation by using the five propositions introduced.