In formulating a focus strategy, the firm needs to achieve a fit between the product/market scope and competition. This paper explores competition antecedents of the firm’s degree of focus, and the moderating effect of market knowledge. The paper emphasizes impacts of the main competitor’s scope and strategic behavior, and competition-based customer access obstacles. To test hypotheses, the study uses data on 430 Swedish firms and contrasts firms with limited and extensive market knowledge. It was found that the competitor’s scope and strategic behavior positively triggers the firm’s focus. The main competitor’s market focus has a greater impact if the firm possesses extensive market knowledge, while the competitor’s strategic behavior affects the firm’s scope only if the firm has extensive experience. The paper discusses theoretical contributions.