The goal of this paper is to examine the effects of a CDSS(Clinical Decision Support System) for drug prescription on organizational performance in medical institutions using POC(Point Of Care) systems. For achieving this goal, evaluation factors for influencing performance of information system were identified by using the performance evaluation model for CDSS. In the results, there was significant causality between each evaluation domain except system quality domain. In addition, the system quality of CDSS for optimal drug prescription has no influence on user satisfaction. But information quality has positive influence on user satisfaction which has also a positive influence on organizational performance.