To explore the following hypotheses: 1) Gas exchange, Organ failure, Cause, Associated disease (GOCA) score, which reflects both general health and the severity of lung injury, would be a better mortality predictor of acute respiratory distress syndrome (ARDS) than acute physiology and chronic health evaluation (APACHE II) or simplified acute physiology score (SAPS II), which are not specific to lung injury, and lung injury score (LIS) that focuses on the lung injury; 2) the performance of APACHE II and SAPS II will be improved when reinforced by LIS, we retrospectively analyzed ARDS patients (N=158) admitted to a medical intensive care unit for five years. The overall mortality of the ARDS patients was 53.2%. Calibrations for all models were good. The area under the curve of (AUC) of LIS (0.622) was significantly less than those of APACHE II (0.743) and SAPS II (0.753). The AUC of GOCA (0.703) was not better than those of APACHE II and SAPS II. The AUCs of APACHE II and SAPS II tended to further increase when reinforced by LIS. In conclusion, GOCA was not superior to APACHE II or SAPS II. The performance of the APACHE II or SAPS II tended to improve when combining a general scoring system with a scoring system that focused on the severity of lung injury.