本文以2007年至2012年臺灣非金融業上市櫃公司為樣本，探討下列議題：自願設置審計委員會之公司特質、自願設置審計委員會的股價反應，以及設置審計委員會對財務報表品質之影響。由於臺灣上市櫃公司股權結構集中、存在控制股東，本文以Claessens等人（2002）提出控制股東之正的誘因效果及負的侵占效果，來分析股權結構對於自願設置審計委員會的影響。實證結果支持替代假說，當控制股東現金流量權較低、投票權與現金流量權偏離較大，公司越有可能自願設置審計委員會。再者，本文發現投資人對於自願設置審計委員會持以正面態度，存在顯著正的累積異常報酬，並且累積異常報酬與審計委員會成員之財務、會計專業比例存在顯著正向關係。最後，部分研究結果顯示設置自願審計委員會能夠降低盈餘管理幅度。

In this paper, we use 2007-2012 non-financial listed companies in Taiwan as sample and discuss the following issues: the characteristics of the companies that volunteer to set audit committee, the reaction of stock price and the impact on the financial reports of those companies. Because of the existence of concentrated ownership structures and controlling shareholders in Taiwan's listed companies, we analyze how the ownership structure affect the setting of audit committee by using the controlling shareholders' positive incentive effect and negative entrenchment effect (Claessens et al., 2002). The empirical result supports the substitution hypothesis. It means that when a company's controlling shareholders' cash flow rights is lower or the deviation between voting rights and cash flow rights is larger, the company are more likely to set audit committee. Furthermore, we find that the investors hold positive attitude to the companies which volunteer to set audit committee. There are positive cumulative abnormal returns of those companies and the relationship between cumulative abnormal returns and the professional proportion (experts of Finance or Accounting) of the audit committee is significant positive. Last but not least, part of the results shows that setting audit committee could lower the range of earnings management.