Service is a concept difficult to define. It has been extensively used in different contexts. According with literature a service can be seeing: as an activity or as an output of a process.By service customization we mean the definition and adaptation of a service according to the customer’ requirements, when this customization process is carried out in a systematic way.A company can respond to user needs diversity offering services than can be customized easily, and/or increasing the service variety offered to the market. The increasing in the service offer variety raises also the variety and complexity in the company transactions that involves cost increments for these transactions. Therefore, the challenge will be to extend the range of services offered to the market maintaining the efficiency, that is similar to the Mass Customization concept.