Question answering systems retrieve information from documents in response to queries. Most of the questions arewho-andwhat-type questions that deal with named entities. A less common and more challenging question to deal with is thewhy-question. In this paper, we introduceLemaza(Arabic forwhy), a system for automatically answeringwhy-questions for Arabic texts. The system is composed of four main components that make use of the Rhetorical Structure Theory. To evaluateLemaza, we prepared a set ofwhy-question–answer pairs whose answer can be found in a corpus that we compiled out of Open Source Arabic Corpora.Lemazaperformed best when the stop-words were not removed. The performance measure was 72.7%, 79.2% and 78.7% for recall, precision andc@1, respectively.