Purpose -The purpose of this paper is to measure service quality in a national library from users' views, based on gap analysis model by using the LibQUAL þ t tools. Design/methodology/approach -The study was done using a LibQUAL þ t survey. In this research, service quality has survived in three dimensions: Affect of Service, Information Control, and Library as Place in three levels -"minimum", "perceived levels of services" and "desired level". Statistical population of this research included all users (female and male) who use different parts of the National Library of Iran (NLAI) in the year 2010. Due to the high volume of population and time & budget restrictions, 332 people formed the sample size.Findings -Findings showed that from users' views, librarians could not meet minimum users' expectations except in some cases. Library resource quality in perceived level of service is less than their expectations minimum. In other words, library resources could not meet minimum expectation and there are more gaps until desired level. Library as Place dimension has more quality than the two other dimensions, but NLAI place quality in perceived level is less than users' expectation minimum. Of course there is a little gap with perceived level in this dimension. Practical implications -The similarity in some results of LibQUAL þ t in academic libraries and national library implies that perhaps LibQUAL þ t tool is applicable for measuring library services in different type of libraries. Originality/value -Using the LibQUAL þ t Survey has helped the national library in Iran to better serve its main user groups and showed that the translated and domesticated version of LibQUAL þ t can be reliably implemented in different type of libraries.