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Nowadays, the issue of service quality for service-provider organizations specifically banks is of considerable importance. The service-provider organizations (specifically governmental banks) are aware from the necessity of getting satisfaction of customer and assessing quality of services. In this research, we evaluate and analyze the gap of expected and current service quality. In fact, the gap between customer´s expectations of bank services and customers perceptions is assessed based on the hierarchical service quality model (HSQM), which has been introduced by Brady and Cronin in 2001. To do this, customers of Keshavarzi Bank are given as statistical population and a sample with 384 people is extracted from Tehran Keshavarzi Banks using Krejcie-Morgan Table and Cochran formula. The results show that just in two dimensions of HSQM namely «waiting time» and «valence», there is no significant difference between expectations and perceptions, but there are gaps among expectations and perceptions in the other dimensions.