: The capability to easily find useful services becomes increasingly critical in several fields. In this paper we argue that, in many situations, the service discovery process should be based on both behavior specification (that is the process model which describes each composite service) and quality features of services. The idea behind is to develop matching techniques that operate on process models and allow delivery of partial matches and evaluation of semantic distance between these matches and the user requirements. To do so, we reduce the problem of service behavioral matching to a graph matching problem and we adapt existing algorithms for this purpose. The matching algorithm is extended by a flexible quality evaluation procedure which checks whether a given service is worth to be delivered or not.