Through history, the mission of the librarian has been the same one: to provide information that the user needs. The service of reference facilitates the access to the information and that helps the user to locate it. But this service has undergone changes throughout the time, and it has been seen specially affected by the advance of the technology. In this article, the author considers some common aspects in developed countries and our country; and also, he provides some useful elements to help to the professional of BCI in the performance of his work like reference librarian to provide an efficient service to the user. Finally he concludes saying that the reference service needs to concentrate in the particular necessities of the user, and not to group.