It is essential that web designers understand what users expect of web services, how they perceive service quality dimensions such as security, usability and information quality, and which ones they value the most. In this study, the users' service quality perceptions of two different web sites were investigated. Data were obtained from 1,900 users of web sites of a for-profit online bookstore and a not-for-profit national information center through the E-Qual Index that was administered online. Findings of the study indicate that users of both for-profit and not-for-profit web sites attach more importance to the "trust" and "quality of information" dimensions as web service quality indicators. Users' expectations should therefore be regularly measured to review the design and information structures of both for-profit and non-profit web sites.