It has become increasingly common to use the project as a form of organization when implementing public policies. Previous research has identified political, administrative and organizational motives behind this trend towards more project-based organizations within the public administration. The problem is that project-based organization carries inherent problems and special challenges when these projects are supposed to be implemented in permanent agencies and organizations. The purpose of this paper is to identify problems and challenges that public administrations face when ‘the project organization’ is used as a structural form of organization in implementing different kinds of public policies. The article takes its starting point in the policy implementation research and especially in Matland’s conflict-ambiguity model. This research tradition is complemented by a review of research on temporary organizations, which draws attention to some inherent and significant characteristics of project organizations, that is the concepts of entity, relationship and time. Our analysis shows that the use of project organization puts special demands on the players involved, and if these are not taken into account, there is a high risk that projects designed to bring about social change will not produce the effects that policymakers and citizens expect.