In this chapter, we examine the differences between software maintenance and software development from a service point of view, and the consequences thereof for the maturity of software maintenance organizations. We argue that software maintenance can be seen as providing a service, whereas software development is primarily concerned with the development of products. Differences between products and services affect the way in which customers assess their respective quality. In particular, service quality is assessed in two dimensions: the technical quality — what the result of the service is — and the functional quality — how the service is delivered. Consequently, customers will judge the quality of software maintenance differently from that of software development. This in turn means that to deliver high quality results in software maintenance, both the functional quality and the technical quality dimension are important.