Benefits can take a variety of forms, for example financial/material (profits, working space, and increased transport capacity), or more intangibly (image and knowledge development). The costs of cooperation can be one-time only (preparation, adaptation of the internal organization), or recurring (organizational coordination , adaptation and tuning of substantive objectives). But what is important is the added value of synergy, i.e. being able to develop a product with characteristics that would not have been available without a PPP. Cooperation , however, implies an increase in the number of participants. Also, in partnerships, the actors are usually dependent upon each other. These two basic conditions create problems (see, for example, Emerson, 1962; Scharpf, 1978; Rogers and Whetten, 1992; Klijn and Teisman, 2000). Network Governance This problem of cooperation can be explored through the network perspective on governance, which assumes that policy is developed and implemented in networks of organizations (see, for example, Kickert et al., 1997; Klijn and Koppenjan, 2000). Policy networks can be defined as 'changing patterns of social relationships between interdependent actors which take shape around policy problems and/or clusters of resources and that are formed, maintained and changed by an ecology of games'. Networks emerge and continue to exist because actors are dependent on each other. Actors cannot achieve their objectives without resources which are possessed by other actors. Thus, networks are characterized by a limited substitutability of resources, which ensures that