The purpose of this study is (1) to develop a conceptually integrated model of IT capability comprising hierarchically structured lower capabilities, and (2) to investigate the impacts of IT capability on firm performance. To do this, the study defined IT capability as a third-order factor model and identified three conceptual dimensions of IT capability IT resource integrating capability, IT infrastructure flexibility, and IT personnel expertise. The relationships between IT capability and firm performance are assessed with 243 firm level data using LISREL. The results of confirmatory factor analysis (CFA) demonstrated that the constructs is highly reliable and valid. Further, we found that IT capability not directly but indirectly affects firm performance through the impacts on business processes.