The decision to invest in information systems can be considered as one of the major challenge that most organizations may face nowadays. Even if Moroccan public large companies are investing huge amount of resources in adopting ERP tools, they are giving little attention to the factors behind this decision. The problem of this article is to determine the criteria that need to be taken by the Moroccan public large organizations in order to invest in information systems? Too many companies and executives cannot answer to these questions and most of them have no clearly defined decision procedures to decide on their investments in technology and to manage it. The aim of this article is to develop a conceptual model related to the Moroccan context based on exploratory interviews and models proposed by previous authors regarding the specificity of Moroccan context. As a preliminary result, we've found that the technological, organizational and environmental contexts have a great influence on the decision to invest in IS, but with different intensity.