Several authors have documented a shift from traditional bureaucracies to collaborative arrangements with joint public and private involvement. This article studies the impact of this shift on accountability. We conclude from our explorative case analysis of Public-Private Partnership (PPP) policy in Flanders (Belgium) that there is an accountability paradox. Many prominent players in the policy arena point to serious shortcomings in the accountability of complex PPPs. Yet, with the introduction of PPPs, the number of accountability mechanisms did increase rather than decrease. This remarkable inconsistency between accountability as a tool and as a result is the main focus of this article. How can we avoid that accountability gets lost in the diffusion of public and private responsibilities?