Online reviews have become a popular method for consumers to express personal evaluation about products. Ecommerce firms have invested heavily into review systems because of the impact of product reviews on product sales and shopping behavior. However, the usage of product reviews is undermined by the increasing appearance of shill or fake reviews. As initial steps to deter and detect shill reviews, this study attempts to understand characteristics of shill reviews and influences of shill reviews on product quality and shopping behavior. To reveal the linguistic characteristics of shill reviews, this study compares shill reviews and normal reviews on informativeness, readability and subjectivity level. The results show that these features can be used as reliable indicators to separate shill reviews from normal reviews. An experiment was conducted to measure the impact of shill reviews on perceived product quality. The results showed that positive shill reviews significantly increased quality perceptions of consumers for thinly reviewed products. This finding provides strong evidence about the risks of shill reviews and emphasizes the need to develop effective detection and prevention methods. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]