Formulating governmental policies for the wider public cannot be an internal process. Embedding openness and participation principles in the policy formulation process can lead to initiatives that re-spond to the real needs and address the real challenges in a policy domain. This paper presents an overview of participation approaches in policy formulation and analyses the structured co-creation process applied by the Greek government to develop the National Action Plan on Open Government. The analysis of the bottom-up participatory approach reveals new insights into the new role of government ‘as a platform’ towards the development and evolution of Government 3.0. The new communication channels, innovative collaboration procedures and digital tools that enabled the active participation of the relevant actors in the policy formulation process suggest a co-creation approach which can be of wide applicability to other policy domains. The paper also addresses the important but under-estimated challenge of actively involving the relevant actors in the implementation of a co-created public policy. The analysis suggests an approach according to which civil society organizations are effectively engaged in the full life cycle of a public policy and take an active role within its implementation.