近年來，我國政府大力推動海外企業來台上市，成效亮眼。在這股熱潮下，為了解海外企業第一上市新股和第二上市台灣存託憑證於我國資本市場掛牌後的表現，本研究針對2009年四月至2010年十二月間，外國與本國發行人在台灣證券交易所新上市之股票和台灣存託憑證進行實證分析。除檢定其是否存在異常報酬外，並綜合過往文獻、相關法令規範及迴歸分析結果，探討影響其異常報酬的可能原因。本研究主要發現如下： （1）國內外企業在台新上市股票及台灣存託憑證均具有顯著的期初異常報酬，其高低依序為－海外企業第一上市新股、國內企業新上市股票、海外企業第二上市台灣存託憑證。 （2）台灣存託憑證期初異常報酬的成因並非來自於承銷價格的低估，而是來自於投資人對於蜜月行情的過度反應。其主要證據為－平均達3%的發行溢價、蜜月期結束後顯著為負的累積異常報酬、及對期初異常報酬最具影響力的示範效果因子。 （3）國內企業在台新上市股票期初異常報酬的成因主要來自於承銷商與發行公司資訊不對稱所造成的承銷價格低估。其主要證據為－新股上市後穩定且接近1.5%的累積異常報酬、及對期初異常報酬最具影響力的折價幅度因子。 （4）海外企業來台第一上市新股異常報酬的成因可能部分來自於發行公司與投資人資訊不對稱所造成的承銷價格低估；部分則可能來自於投資人對蜜月行情的過度反應。其主要證據為－蜜月期結束後為負的累積異常報酬、及海外企業來台第一上市新股與國內新上市股票的合併資料迴歸中，群體效果、中籤率與海外第一上市名目變數等顯著影響因子的間接支持。 / This study attempts to investigate the different patterns of the abnormal returns of Taiwan listings by foreign issuers and IPOs by domestic issuers, for the period from April, 2009 through December, 2010. Of particular interest is to examine the determinants of the abnormal returns. The major findings of the study are as the follows: (1)Empirical results indicate that all Taiwan listing stocks, including IPOs by foreign and domestic issuers and TDRs, have significant abnormal initial returns. Among them, IPOs by foreign issuers show the highest abnormal initial returns while TDRs show the lowest. (2)Evidences like the negative CARs, the average 3% premium of TDR issuance and the demonstration effect suggest that investor overreaction could be a major factor contributing to TDRs’ significant abnormal initial returns. (3)Evidences also suggest the under-pricing by the better-informed underwriters may cause significant abnormal initial returns of IPOs by domestic issuers. The IPO discount is discussed as an in-depth demonstration. (4)The study assumes that the significant abnormal initial returns of IPOs by foreign issuers partly result from the under-pricing as a signal to attract investors, and partly result from investor overreaction.