Despite compelling evidence that top management support promotes information technology project success, existing research fails to offer insight into the antecedents of top management support of such projects. This gap in the literature is significant since the exploitation of information technology offers organizations unique opportunities for growth and competitive advantage, and failure to understand the determinants of top management support may result in missed opportunities and poor allocation of valuable organizational resources. Indeed, a recent study by the Standish Group found that only 37% of information technology projects are considered successful, with 21% of projects considered a failure and 42% of projects considered challenged. Such statistics, combined with overwhelming evidence that top management support is one of the most important drivers of project success, clearly indicate that a better understanding of the factors that influence top management support is urgently needed. This dissertation aims to address this issue by integrating insights from the information systems and top management team literatures to develop and empirically test a comprehensive model of the determinants of top management support. A decomposed approach to the theory of planned behavior (Ajzen, 1991) is followed to identify the most salient factors that are likely to influence a top manager's motivation to support a given information technology project. The resulting model is operationalized and tested through an empirical study of 283 senior executives. The findings of the research indicate that top management support is significantly influenced by the strategic and informational benefits of a project as well as by forces of self-justification, internal organizational pressures, and mimetic pressures. Finally, the broader implications of the study and suggestions for future research are discussed. [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/en-US/products/dissertations/individuals.shtml.]