過去文獻大多僅以總經理與董事長是否為同一人作為判斷總經理是否兼任董事長之標準，然台灣企業以中小型家族企業為主，常發生董事長與總經理或CEO雖不為同一人，但彼此互為配偶或具有二親等以內之親屬等關係，且若總經理不兼任董事長，但兼任董事，則仍有可能對董事會產生一定程度之影響力，故本研究考慮總經理兼任董事之影響力及總經理與董事長之二親等或配偶關係，期能突顯名義上與實質上兼任情況的差異。本研究主要探討總經理是否兼任董事長與公司績效的關聯性，並檢視此關係是否會因不同公司特性而有影響，如公司家族持股比例、組織複雜程度及產業類別等，並探討若設置獨立董監，是否可以減緩代理問題。本研究萃取台灣上市公司之資料，樣本數為3,619筆。實證結果指出在考慮台灣目前政策未納入的總經理兼任董事及總經理與董事長之間的二親等或配偶關係後，雙重性-績效關係確實存在負向效果且受到公司家族持股比例以及產業之不同而有影響。家族持股比例高或電子業較適合董事長兼任總經理之經營模式。再者，可利用設置獨立董監制度之方式減緩代理問題。

This paper seeks to examine the relationship between chief executive officer (CEO) duality and firm performance. We also investigate whether the duality-performance relationship is affected by firm characteristics, including the family ownership, firm complexity, and industry. We discuss whether the agency problem could be mitigated for a company of the combination of the position of CEO and director has independent director and supervisor system. We propose and test hypotheses with a sample of 3,619 public companies in Taiwan. Our results indicate that after consideration of the combination of the position of CEO and director, and the second-degree relatives or the marriage relationship of CEO and the chairman of the board, the relationship between duality and firm performance become significant. Our results indicate that when family ownership is high, the combination of two roles is beneficial to the firm, and the combination of two roles is also beneficial to the firm of the electronic industry. And, agency problem could be mitigated for a company of the combination of the position of CEO and chairman has independent director and supervisor system.