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Nowadays, there are many organizations searching for more effective way to compete in the fast growing markets. Internal services for these companies play an undeniable role in orienting the competition. The managers’ attentions have been drawn to the internal services that produce competitive advantages. One of these services is Information Technology which establishes a major quota of cost portfolio for the organizations. Due to those above mentioned facts, evaluating the performance of IT departments become a very considerable aspect for administrating the organizations. In this paper, at first we review three known models in service quality measurement, namely SERVQUAL, SERVPERF, and Nor med Quality. Among these models we choose SERVQUAL for measuring service quality of IT departments. In next step, we measure IT service quality of one of the Iranian public transportation companies using SERVQUAL. Based on a gap analysis, we offer recommendations to improve the IT service quality for the company. In this paper IT affects on SERVQUAL dimensions and new dimensions are presented using factorial analysis.