Despite a general assumption that Information Technology is necessary for most business processes, the business value of IT is the subject of debate and controversy in theory and practice. Based on the Resource-based View of the Firm (RBV) and literature on IT business alignment this thesis theoretically evaluates and empirically validates the basic mechanisms that link IT to performance. Employing case studies and a survey in parallel, this work identifies a set of factors and their interrelationships affecting firm performance. The results extend our theoretical knowledge on how to use the IT resource and help managers to make better decisions on using IT, thereby enhancing an organization's performance.