Both academics and practitioners have a growing interest in information technology (IT) value. This is particularly important in cases of systems such as enterprise resource planning (ERP), as the use of these systems involves significant investment. In this study we seek to measure and examine determinants of ERP use and value. Based on the diffusion of innovation (DOI) literature to explain ERP use and resource-based view (RBV) theory to explain ERP value, we develop a research model, on which nine hypotheses are postulated for measuring ERP in post-adoption stages and its consequences on Portuguese small and medium enterprise (SME) performance. The model was tested through structural equation modelling (SEM) on a dataset of 134 firms web-surveyed. We find that compatibility, best practices, complexity, efficiency, training, and competitive pressure are important determinants of ERP use. Together with use, collaboration and analytics capabilities will contribute to "ERP value'. Even though this study provides insight into how SMEs use and extract value from ERP, unlike the typical focus on ERP adoption reported in the literature, this study focuses on post-adoption stages, linking actual usage with value creation.