In this paper, we presented our newly developed computer-aided liver surgical planning system for patient-specific treatments by using the patient's CT volumes. The system is composed of three modules, liver segmentation, vessel extraction, and visualization & interaction modules. It can prepare a virtual environment for patient-specific liver surgical planning and simulations. We also developed an original visualization library, which is based on GPU (graphics processing unit) computing for real-time interaction and visualization. The effectiveness of our system was evaluated by surgeons with liver surgery simulations.