The IRI government in recent years has developed and implemented a particular measure titled "clients honour in public sector" based on valued principles and the scientific outcomes of "demoncracy" and customer-orientation". The measure's imprementatin has brought about many achievements. However, lacking right procedures to measure and evaluate its degree of effectiveness resulted in some drawbacks. The study is conducted to introduce and apply the gap analysis model or serqual in measuring the effectiveness of clients honour in public sector. for this purpose, first some three questionnaires were developed to measure the effectiveness of the clients honour program, following a study on the theoretical principles of assessing service quality as well as clients honour program in public sector. Questionnaires were improved taking into account, the experts points of view, and the validity was tested. The proposed model was utilized at subseribers unit of the Yazd state telecommunication office and the questionnaires were handed out among some 305 clients and the entire staff of the subscribers unit and the data were collected. Nonparametric statistical measures such as Mann-Whimey and Willcoxon and Friedman were used to analyze the colleted data. The study found that there is significant difference between client Perceptins and expectations in all 5 dimensions of client satisfaction. In other words Customer Affairs of Yazd Telecommunication Co has not satisfied its clients in any of quality dimension. And also there is significant difference between client expectations and employee's perceptions only in the empathy. This means that employees perceive clients in Tangibility, Reliability, Responsiveness and Assurance dimensions. Finally there is significant difference between the extents of dimensions' effects on clients satistaction, so decision makers should plan their programmes for improving client satisfaction degree based on importance of each dimension. These results show that application of Gap Analysis Model is a proper tool for measuring the degree of client satisfaction and decreasing the weaknesses of CSM. Finally for decreasing these differences some suggestions are presented.