The purpose of this study was to evaluate the migration of medical image data stored thorough mini-PACS to full-PACS at Yonsei University Medical Center (YUMC). The image data to be migrated were 2.7 TB stored through approximately 4,500 CD archives at Yongdong Severance hospital and 4.7 TB (2:1 compression) stored through 196 digital linear tape (DLT) archives at Severance hospital. Prior to carrying out the migration, principles, methods and expected practical affairs for the migration were discussed and planned to optimize the migration work by considering the cost and the effectiveness of migration work. Migration gateway workstations were set up and a migration software tool was developed. Real migration works were performed based on the results of several migration simulations. Severance hospital decided to migrate all stored image data. The CD image data of 2.7 TB were estimated total 2,250 hr (about 94 days) migration time, but the practical migration work was completed within 3 months by using maximum 5 workstations. The DLT data of 4.7 TB were estimated total 100 days migration time by applying 16 hr working time per day with single workstation, however, the practical migration work was taken 5 months. Meanwhile, 20% of the DLT image data were not able to migrate because the DLT were partially damaged due to frequent access. In conclusion, a migration plan should be carefully prepared by considering the individual hospital environments because the server system, archival media, the network, and the policy of data management may be unique.