Finally, performances that have influence on the success or failure of information system are often argued in literature. They can be classified in eight different dimensions so they include not just the system aspect but also ...the human aspect of information system successfulness. Opinion analysis of users, information technology specialists and managers reveals that there are no significant differences in order and importance of information system successfulness factors between information technology specialists and information system managers, as well as between users and user’s managers. However,the order of factors by importance is significantly different between information technology specialists and users. Therefore, the most important information system successfulness factors are identified.