A growth of data published on the Web is still observed. Keyword-based search, used by most search engines, is a common way of information retrieval on the Web. Subsequently, keyword-based search may provide a huge amount of retrieved valueless information. This problem can be solved by Question Answering System (QAS, QA system). One of the challenging tasks for available QA systems is to understand the natural language questions correctly and deduce the precise meaning to retrieve accurate responses. A significant role of QA and an increasing number of them may cause a problem with selection the most suitable QA system. The general aim of this paper is to provide knowledge-based approach to QA system selection. It should ensure knowledge systematization and help users to find a proper solution that meets their needs. Zdroj anotace: OKCZ - ANOTACE Z WEBU