Purpose: We wished to develop the web based Picture Archiving and Communication System in the emergency room for early decision making in emergency treatment planning at a full PACS Hospital. Materials and Methods: The program tools were Microsoft Visual Studio 6.0 - Visual C++ 6.0, and the Microsoft SQL 7.0 under the Microsoft Windows 2000 operation system. The achievement of images was performed by an auto transport program installed in the ER and the radiology department. Results: The average compression rates were 5:1 for CT and MR, and 20:1 for CR with JPEG 2000 lossy compression. All the images were stored on hard disk for 3 months. The patients’information was displayed for 2 weeks for reducing the security risk. For interdepartmental consultation, patient query by patient hospital number was available. Conclusion: Our Web based ER PACS could be useful system for early decision making for treatment planning in the emergency room because it reduces the risk factors for the security of the Web PACS by using a system independent from PACS in the hospital and minimizing the information patients.