In the last couple of years, Web services have been used in the development of Web systems, which are often composed by interoperable components. These interoperable components cooperate under a Client/Server style to accomplish the application integration and it is aimed to use the service components in several systems. Therefore, the development of such Web services, as high quality and reusable components is a goal to achieve. In this sense, suitable design and modeling techniques can improve the customisation of similar services built by one or more service provider. On the other hand, the development, the management and evolution of many modem software systems rely on the notion of variability and pattern-based approaches as suitable design techniques. In this work we will try to describe how the development of Web systems using Web services can be improved with a suitable description of the variability as a technique for building and customizing similar systems. We will focus on the modelling of variability of Web services from a pattern point of view.