Hospital Information Systems assessment is important to ensure the quality of provided healthcare services. This research evaluates the success of the clinical information system used in the General Hospital “Asklepieio Voulas”. A questionnaire was developed based on the DeLone & McLean information systems success model, and used on February 2020, to record the users’ opinions regarding the information system. The reliability of the questionnaire was tested by applying Cronbach’s alpha analysis, descriptive statistics was calculated for all variables of the questionnaire, and new variables was created to investigate the relationships between the model’s factors. Correlation analysis between the factors and linear multiple regression analysis between some of the factors of the DeLone & McLean success model were conducted 218 users responded to the survey, 56.3% of them were medical doctors, 24.1% nurses, and 19.6% other staff of the hospital. Results highlight that the users of the system are satisfied with it. A77.3% of the participants believe that they perform their work more easily when using the system, while 89.3% of the participants believe that the system is useful in their work. According to the results of the model, system quality and information quality seems to be related with the system usage. Information quality plays the most important role in the use of the system while the system quality plays the most important role in user satisfaction. Based on the users’ opinions, the “Asklepieio Voulas” Hospital Information System can be assumed as successful.