The existing works point out that smaller organisations have been shown to have different technology adoption patterns than large ones. However, it is unclear whether Small to Medium Sized Enterprises (SMEs) and large organisations take decisions for the adoption of integration technologies by focusing on different factors. Moreover, the literature also shows that there is an absence of theoretical models that explain the adoption of Enterprise Application Integration (EAI) and Web Services in SMEs. These research issues, derived from the literature review, are taken into consideration and addressed in this paper, aiming at highlighting any significant difference in the way SMEs and large companies adopt integration technologies. In doing so, the parameters that can be used to explain the adoption of integration technologies in organizations are identified, as nature of organisations, company size, integration needs and time. These are tested through four case studies: a large organization and three SMEs.