The contribution of IT to business performance in the information systems field has been studied from two perspectives: the strategic positioning perspective, which emphasizes the expansion of market dominance, and the resource-based view, which focuses on the conceptualization of a firm's unique resources. Although both perspectives provide theoretical foundations for the relationship between IT and firm value, they have developed independently within the IS literature. However, some researchers have argued that these perspectives are not opposing but complementary. This study aims to examine how IT creates business value. The purpose of this study is to understand and improve the role of IT in firm performance through the complementarity between the two perspectives. More precisely, the research model summarizes the effects of specific IT capabilities, IT support for strategy, and IT support for firm competencies. This study defined IT capabilities as technical and managerial capabilities; set innovation differentiation, marketing differentiation, and low cost IT support as sub-factors of competitive strategy IT support; and established IT support for organizational competency, marketing competency, and technological competency as sub-factors of firm competency IT support. Firm performance was measured by subdividing it into quantitative and qualitative performance. Additionally, to develop a more extended research model, the moderating effects of environmental dynamism and top management support were also examined. To test the proposed research model, a survey was conducted targeting 169 firms appropriate for the research purpose, and the data were analyzed using the PLS approach. The analysis results showed that IT capabilities had a statistically significant effect on both competitive strategy IT support and firm competency IT support. Positive effects were also found in the relationships among competitive strategy IT support, firm competency IT support, and firm performance. However, the effect of firm competency IT support on competitive strategy IT support was found to be non-existent. Regarding moderating effects, environmental dynamism strengthened the relationships between IT capabilities and competitive strategy IT support and between IT capabilities and firm competency IT support, while top management support significantly moderated the relationship between competitive strategy IT support and firm performance but had no effect on the relationship between firm competency IT support and firm performance. The results of this study, which surveyed firms with high IT dependency, suggest that firms need alignment between internal and external business and IT to actually improve performance. Theoretically, this provides empirical evidence in another context for research related to IT business value, and practically, it offers refined insights into business and IT for enterprises, serving as a useful guideline for corporate decision-making.