The purpose of this work is to provide an analysis of the patterns of collaboration between the public and private sectors in relation to the stringent financial obligations imposed to administrations and the analysis takes into account both contractual and corporate-based PPPs. In this perspective, the PPP is a solution that public administrations can take advantage of, in relation to the many benefits provided by the current rules, both in terms of respect for public finances and optimal allocation of risks between administration and firms. Specifically, the investigation is focused on the notions of flexibility and economic risk, to provide a legislative and interpretative fra- mework that takes into account the objectives that administrations must achieve, especially with regard to infrastructure development.