本文探討在兩個廠商交叉持股的數量競爭市場中，廠商在「主動持股」與「被動持股」之間的策略選擇。於被動持股下，收購廠商僅獲得財務回報；而在主動持股下，廠商除了獲得財務收益外，還能對競爭對手的決策施加部分控制，但須承擔監督成本。在假設交叉持股程度與監督成本對稱的情況下我們得到以下結果：在給定監督成本時，隨著交叉持股程度的提高，均衡將從被動持股轉向主動持股，然後再回到被動持股。此外，交叉持股程度的增加可能提升社會福利，顯示所有權結構與社會福利之間的微妙變化。最後，我們放寬對稱性假設以進一步延伸分析。

This study examines firms’ strategic choices between active and passive ownership in a Cournot duopoly with cross-shareholdings. Under passive ownership, the acquiring firm receives only financial returns, whereas under active ownership, it also exerts partial control over the rival’s decisions at the cost of monitoring. Assuming symmetric cross-holdings and monitoring costs, we derive the following results. For a given monitoring cost, the equilibrium shifts from passive to active ownership and back to passive ownership as the degree of cross-ownership increases. Greater cross-ownership can enhance welfare, revealing a nuanced relationship between ownership structure and social welfare. We extend the analysis by relaxing the symmetry assumptions.