The purpose of this paper is to consider how resource-based theory can be used to explain success with the adoption and use of information systems and information technology (IS/IT) in manufacturing Small and Medium-sized Enterprises (SMEs). A number of authors have explored the applicability of resource-based theory to the IS/IT domain, mainly at a conceptual level. Overall they infer that the key differentiators for long term successful IS/IT deployment reside within the internal context of an organisation, based on organisational competences. This paper is based on in-depth case study research in twelve Portuguese manufacturing SMEs. With the objective of trying to understand why and how these factors caused the different success levels of IS/IT adoption identified, the findings were analysed from the perspective of resource-based theory. The analysis of the data suggested that certain combinations of factors, also primarily associated with the internal context, were the determinants of the different levels of success in IS/IT adoption and use.