In today’s business world, there are varieties of information systems such as TPS, DAS, KWS, MIS, DSS, ES, CSCWS, GDSS and ESS. Each plays a different role in organizational hierarchy and decision making process. In this article the authors have selected two main information systems, namely, MIS and DSS. After discussing the decision making process based on each concept, its characteristics, relations, connections of each concept to decision-making process have been determined. At the same time, different models and figures are presented to enrich the discussion and to highlight precisely the status of each MIS and DSS information system in organizational decision making