The present study investigates domestic and foreign cases of library specialization, and specialization policies, areas, and effects in order to delineate future directions for research on the subject. The results of the study indicated that library specialization policies have been implemented in Korea and other countries. In Korea, a short-term policy was implemented in 1998, designating 13 special libraries, nine of which are currently in operation. Regarding types and directions of specialization, specialization of collections was found in many cases. Regional representative libraries were also found to have designated specific subjects they focus individually in terms of collections and services while providing services in subject areas. The future directions include research in qualifications and competence of professionals employed in special libraries, and in user satisfaction and needs to inform libraries' efforts for specialization.