本研究以臺灣1997至2006之上市櫃企業為研究對象，探討企業之盈餘平穩化行為，是否對權益資金成本產生影響，並探討家族企業之盈餘平穩化行為及其權益資金成本。本研究將人為的盈餘平穩化行為分為來自裁決性應計項目及非營業項目之盈餘管理。研究結果發現，臺灣上市櫃公司確實可透過提高企業長期之盈餘平穩性降低權益資金成本。雖然，企業採用非營業項目有高於裁決性應計項目達成之盈餘平穩效果，市場也會察覺兩種盈餘管理行為之風險，導致權益資金成本的提高。但是，當此兩種行為有平穩盈餘時又可達到降低權益資金成本的目的。不管有無考慮家族因素，比較兩種盈餘管理工具對權益資金成本之影響並無太大差異，意即市場無法分辨不同的盈餘管理工具所造成之盈餘平穩化之效果。

This study uses Taiwan listed companies between 1997 and 2006 to examine the effect of the firm's income smoothing behaviors on the firm's cost of equity. This study explores the family firm's income smoothing behavior and cost of equity, which the former is divided into two earnings management tools: discretionary accruals and non-operational items. The findings indicate that for Taiwan listed companies, elevating long-term income smoothing does reduce the firm's cost of equity. Study results suggest that although firms tend to prefer non-operational items to discretionary accruals for achieving the income smoothing effect, the market can detect the associated risks with the two earning management tools, and thus the firm's cost of equity increases. However, using the two earnings management tools for income smoothing can achieve the purpose of reducing the firm's cost of equity. Finally, whether or not family factor is considered, no difference is found from comparing the effect of the two earnings management tools on the cost of equity, that is, the market cannot differentiate the income smoothing effect amongst different earnings management tools.