Fifth, users and information technologies specialists as groups have different opinions about ratings on several factors of information system successfulness. On the one hand, users and their managers assign more importance to output results (services) of information system such as: noticed usefulness, form of output, business effects of computer support, than information technology specialists. On the other hand, it has been shown that managers and specialists for information technologies are more concerned with the environment of information system services (such as: relations between users and information technologies specialists and processing of system alterations demands) than are users. In order for information system to be successful, the management of information system should understand and manage these differences. Also, they should pay more attention to ends of services rather than the middle of the information system during the planning of resources and for mulation of strategies for development and successful functioning of information system.