One of the challenges in delivering e-government services is to design the Web sites to make it easier for citizens to find desired information. However, little work is found to evaluate e-government services in this sense. In addition, current efforts on government Web site design mainly concentrate on Web site features that would enhance its usability, but few of them answers why some Web design is better than others to facilitate citizens' information seeking. This paper aims to contribute to both aspects: it equips government agencies with a model that can not only evaluate their Web-based e-government services, but also helps them understand why their Web sites succeed or fail to help citizens find needed information. In addition to the model itself, instruments for applying this model are also developed.