This study was conducted to assess the amount of nursing services for psychiatric inpatients and to estimate psychiatric nursing costs by using the RBRVS. Full details of medical services, including physician and nursing services, for psychiatric inpatients were surveyed and data of general characteristics of hospitals and patients were also collected. The cost of nursing activities was estimated by the multiple conversion factor which was drawn from the Korean RBRVS Development Project to the RBRVS score of each nursing activities, which was drawn from the results of Korean Nurses Association (KNA)'s projects about nursing RBRVS development and cost of nursing activities. The data about 89 inpatients from 3 general hospitals with psychiatric departments were analyzed. The total cost of nursing activities for each patient per admission day was from KRW 22,185 to KRW 27,954 by hospital, and KRW 25,220 in average. The percent of nursing cost to the total cost of medical services was from 36% to 48% by characteristics of patients and 41.4% in average. The cost of nursing activities estimated in this study was between the existing NHI fee schedule and the one suggested by KNA. It is considered as appropriate and acceptable level compared to the total amount of medical services. In the process of KNA's activities to get nursing fee in NHI fee schedule, results of additional studies to estimate the cost of nursing activities balanced with total cost of medical services in every departments should be found and utilized.