BPEL has emerged as the industrial standard language for modelling behavioral aspects of web services. To support business partners in dynamically and flexibly binding their services together, different BPEL processes need to be efficiently matched. This paper identifies and defines various types of structural matching for BPEL processes. The matching definitions are based on heuristics: they take behavioral interaction aspects of the compared services into account, but abstract from irrelevant syntactical differences. Since the definitions are structural, they can be efficiently computed, and thus are useful to support dynamic and flexible binding of services. The approach is illustrated with an example from an existing business scenario.