PURPOSE: To determine and compare the perception among nurses and doctors of the roles and tasks of critical care advanced practice nurses (APNs) in order to establish standardized and formally agreed role criteria for such critical care APNs. METHOD: This study measured and analyzed the necessity of each of the roles and tasks of critical care APNs, as perceived by nurses and doctors, through a survey of 121 participants: 71 nurses in 7 intensive care units (ICUs) at a general hospital in Seoul, and 50 doctors who used ICUs. Data collection utilized a questionnaire of 128 questions in the following fields: direct practice (79), leadership and change agent (17), consultation and collaboration (15), education and counseling (11), and research (6). RESULTS: Both the nurses' and the doctors' groups confirmed the necessity of critical care APNs, with doctors who frequently used ICUs indicating a particularly strong need. As for the priority of each role of critical care APNs, the nurses considered direct practice to be the most critical, followed by education and counseling, research, consultation and collaboration, and leadership and change agent. The doctors also considered direct practice to be the most critical, followed by education and counseling, consultation and collaboration, research, and leadership and change agent. There was a statistically significant difference between how the two groups regarded all the roles, except for the consultation and collaboration roles. As for the necessity of each role of critical care APNs, the nurses considered research to be the most necessary, followed by education and counseling, consultation and collaboration, leadership and change agent, and direct practice. The doctors, on the other hand, considered education and counseling to be the most necessary, followed by research, consultation and collaboration, leadership and change agent, and direct practice. The responses of the two groups to all the roles, except for education and counseling roles, were significantly different. CONCLUSION: Nurses and doctors have different perceptions of the roles and tasks of critical care APNs. Thus, it is necessary for the combined nursing and medical fields to reach an official agreement on a set of criteria to standardize for the roles and tasks of critical care APNs.