Understanding post adoption behavior has emerged as an important issue in IS research. Organizations have invested in a plethora of Information Systems (IS) and the benefits that can be gained from these systems depend on their usage. Prior research has examined factors that impact users’ intention to continue using the IS. However, comprehending post adoption IS usage behavior has not received much attention. Building on TAM and IS success model, this study proposes that information quality and system integration influence perceived IS usefulness which will then drive post adoption usage of the IS. Post adoption IS usage is conceptualized as a broad concept that includes extended usage and exploratory usage. Data (N = 1032) was collected to test the model, in the context of a web-based student information system that students use to manage their academic work. The results show that at the post adoption stage, perceived IS usefulness is a good predictor of extended usage and exploratory usage. However, surprisingly IS usefulness was found to explain a much larger variance in exploratory usage. Information quality and system integration were found to influence IS usefulness. However, information quality also has a direct affect on extended usage, while system integration directly influenced exploratory usage. Assessment of the moderating role of gender and internet experience on model relationships reveals interesting insights. Implications are drawn for future research and practice.