Information-management systems of an enterprise’s resource planning, such as ERP, CRM, SCM and so on, are an integral element in the management structure of a modern organization. Developers of such software products conduct continuous improvement of software functionality, introduce various elements of analysis, elements of artificial intelligence, and unify the information exchange system of software products of various developers. In order to improve business results and acquire the economic advantage over competitors, organizations have to consider the possibility of updating or replacing the operated information management systems. However, the analysis of the results of such investment projects conducted by various independent experts reveals many negative results of implementation. The article is devoted to the study of possible problems of assessing the economic efficiency of informationmanagement systems and the study of methods of their effective implementation. The methodological basis of the study is grounded in the analysis of various theories of assessing the economic efficiency of information-management systems in the scientific research of the most famous authors. The main sources and mechanisms of the occurrence of economic efficiency arising during the implementation of projects are considered. An approach to calculating economic efficiency based on the analysis of information support of the organization is proposed. The results of the study can be used at the decision-making stage on the implementation or modernization of information-management systems, as well as to improve functional abilities and increase the economic efficiency of existing systems.