The present investigation was carried out using LibQual software in order to evaluate the user view on the quality of services offered by the Central Library of Tarbiyat Modarress University. It was conducted at three levels of minimum, maximum and real. The sample was drawn from in-house and outside users, including graduate students and faculty members. Findings indicated that in most cases there is a difference between users’ expectations and the services offered by the library. Users’ demands are somewhat satisfied at minimum level, but there is a significant gap with respect to desired level and users’ maximum expectations. Among different user groups, whether faculty or student, there is a significant difference with respect to the gap between the expectations and the services offered. There had been no significant difference of opinion among in-house and outside users regarding quality measures dealing with staff and the library space. There is however a significant difference regarding the quality of sources helf.   By using the factor analysis method, four factors were identified as contributing factors to the quality of library services. These were “availability and accessibility of sources”, “Availability of qualified and diligent staff”, “Suitability of space for individual or group study and learning” and “Ready Access to Information”.