Objectives: This study analyzed the effects of computerization of medical information systems and a hospital payment scheme on medical care outcomes. Specifically, we examined the effects of Electronic Medical Records (EMRs) and a diagnosis procedure combination/per-diem payment scheme (DPC/PDPS) on the average length of hospital stay (ALOS). Methods: Post-intervention changes in the monthly ALOS were measured using an interrupted time-series analysis. Results: The level changes observed in the monthly ALOS immediately post-DPC/PDPS were –1.942 (95% confidence interval [CI], –2.856 to –1.028), –1.885 (95% CI, –3.176 to –0.593), –1.581 (95% CI, –3.081 to –0.082) and –2.461 (95% CI, –3.817 to 1.105) days in all ages, <50, 50–64, and ≥65 years, respectively. During the post-DPC/PDPS period, trends of 0.107 (95% CI, 0.069 to 0.144), 0.048 (95% CI, –0.006 to 0.101), 0.183 (95% CI, 0.122 to 0.245) and 0.110 (95% CI, 0.054 to 0.167) days/month, respectively, were observed. During the post-EMR period, trends of –0.053 (95% CI, –0.080 to –0.027), –0.093 (95% CI, –0.135 to –0.052), and –0.049 (95% CI, –0.087 to –0.012) days/month were seen for all ages, 50–64 and ≥65 years, respectively. Conclusions The increasing post-DPC/PDPS trends offset the decline in ALOS observed immediately post-DPC/PDPS, and the observed ALOS was longer than the counterfactual at the end of the DPC/PDPS study periods. Conversely, due to the downward trend seen after EMR introduction, the actual ALOS at the end of the EMR study period was shorter than the counterfactual, suggesting that EMRs might be more effective than the DPC/PDPS in sustainably reducing the LOS.