Rob Kling strongly advocated the term Social Informatics. He demonstrated that equipment, equipment vendors, technical specialists, upper-level managers, ICT policies, internal funding, and external grant funding with the people who will use information systems in the course of other work are not simply a static list but are interrelated within a matrix of social and technical dependencies. In Information Systems there has recently been heated debate about the core content of the discipline. In this paper we study whether Social Informatics and Information Systems are similar or not. According to the broad view on Information System, they appear quite similar. The few differences we identified are in research approaches, when most Social Informatics researches use intensive case studies while most Information System researches surveys. Such minor differences do not support the view that these two sciences should have different names. The researches in both sciences seem to believe that people’s behavior can be predicted, but we demonstrate that this is not true. Hence we propose that theories with people as a component must be adjusted accordingly in both sciences.