併購相關的實證研究大多聚焦於併購資訊洩漏與併購後之長期績效表現的議題，本研究則運用Chen, Kao, Tsao and Wu（2007）所提出公司治理指數並結合事件研究法，以檢視健全的公司治理機制是否能減輕併購資訊洩漏所產生之異常交易的現象。實證結果顯示公司治理較差的公司在併購訊息宣告前已出現嚴重的資訊洩漏情形，而良好的公司治理的確可以減輕併購宣告前之資訊洩漏的問題。另外，公司治理較佳的公司，在併購宣告後出現正的異常報酬，此結果顯示良好的公司治理亦有助於提升企業併購後之經營績效。最後，迴歸分析結果則指出，合適的董事會規模與併購宣告後之異常報酬存在顯著的正向關係。

Substantial empirical research regarding merger and acquisition (M&A) has focused on issues such as information leakage about M&A and long-term performance after M&A. This study uses the corporate governance index proposed by Chen, Kao, Tsao and Wu(2007) and the event study method to investigate whether sound corporate governance mechanisms reduce abnormal transactions caused by information leakage. Empirical results show that there exists a serious information leakage prior to the M&A announcement for the firms with poorer corporate governance. Also, good corporate governance indeed reduces information leakage prior to the M&A announcement. Additionally, there are positive abnormal returns after the M&A announcement for the firms with better corporate governance, implying that good corporate governance helps enhance the post-merger operating performance. Finally, regression analysis points out that there is significantly positive relationship between appropriate broad size and abnormal returns after the M&A announcement.