In this chapter we look into earlier empirical research on the barriers to electronic commerce (EC) adoption and diffusion for small and medium sized enterprises (SMEs). We explore research conducted in the context of information and communications technologies (ICT) in general, as well as EDI and Internet based EC. What we are interested in is whether these barriers are something new created by the new wave of Internet based technologies. We divide the barriers, inhibitors or factors slowing down the diffusion of new technologies found in previous literature into those internal to an organization, and those imposed by external forces. The basic premise of this chapter is, that technologies advance or change, but the barriers for SMEs to adopt them do not. The authors hope that understanding this will help researchers, small companies and policy makers to move on and do something active to reduce such barriers.