The success of Web services technology depends heavily on the effective discovery and sharing of services in distributed environments using various registries. These tasks should take into account both functional and non-functional properties (NFP) of a service. Such properties may be for example: execution time, reliability, security, cost or provider’s reputation. However, currently known approaches focus mainly on the functional attributes of Web services and there is an ongoing discussion on the scope and methods that should be used to express the non-functional side of WS. This article presents an ontology of non-functional properties and shows, on the example of the WebSter registry, how it may be used within the WS discovery process in distributed environments.