A virtual enterprise results from a temporary agreement among some enterprises, which decide to cooperate together into a given value chain for a limited time horizon. The crucial point in the development of said network is to search for partners and organize interactions among firms. In practice, a first problem has to be approached each time a re-organization of the network can be applied, by either including a new component firm or leaving a component to be independent. A second crucial problem refers to an individual enterprise, which has to decide about its own convenience to be a partner in a newtrok. The paper aims to define some criteria for supporting these two design problems. The scope is to have simple conditions able to evaluate if cooperation among potential partner firms could be successfully stipulated.