When multiple web services exist that perform identical tasks, non-functional attributes must be considered in order to choose the best service. Quality-of-service (QoS) attributes are often used to differentiate functionally redundant web services. However, ranking services according to QoS attributes is a complex problem. Additionally, the use of test data to establish those QoS ratings does not always yield accurate results. Therefore, this paper proposes a method that utilizes opinion mining techniques to extract information about the QoS attributes of a web service based on free-text user reviews. This method not only has the advantage of using real-world data rather than test data, but it also ensures that a variety of use cases are tested that would be common in the everyday usage of that service.