不完全給付與物之瑕疵擔保，理論與實務均極為重要。針對不完全給付與買賣物之瑕疵擔保之競合關係，及不完全給付與承攬物之瑕疵擔保之競合關係，最高法院更分別作有77 年度第7 次及96 年度第8 次民事庭會議決議。 關於不完全給付與買賣物之瑕疵擔保之競合關係，最高法院裁判尚有歧異者為：買賣契約成立前，標的物即已存在瑕疵（即所謂之「約前瑕疵」），而出賣人因故意或過失以該物交付於買受人者，買受人得否主張出賣人除應負物之瑕疵擔保責任外，亦應負不完全給付之債務不履行責任？本文以為，此項爭議，並非最高法院77 年度第7 次民事庭會議決議所欲解決之問題，自不得依該決議而謂買賣標的物之瑕疵係於契約成立前即已存在者，出賣人僅依瑕疵擔保規定負責，而不負不完全給付責任。而且，依據不完全給付之理論，及本於買受人利益之保護，依本文所信，在「約前瑕疵」之情形，應如同「約後瑕疵」（即買賣標的物之瑕疵係於契約成立後始發生）處理，而允許買受人既得主張物之瑕疵擔保，亦得主張不完全給付。 關於不完全給付與承攬物之瑕疵擔保之競合關係，最高法院作成96 年度第8 次民事庭會議決議。依該決議，因承攬工作瑕疵所生之損害，應區分為瑕疵給付之損害與加害給付之損害，且民法第495 條第1 項所稱之損害，不含加害給付之損害，但該條項所定之損害賠償請求權已罹於民法第514條第1 項規定之一年短期時效者，定作人就同一損害，不得另依民法第227條不完全給付規定請求賠償。此項決議，力圖兼顧定作人與承攬人之利益，用心良苦，甚值敬佩。惟問題在於，承攬工作之瑕疵給付損害與加害給付損害，實務上如何區分？此外，最高法院裁判透過96 年度第8 次決議，將修正後之民法第514 條第1 項，賦予溯及既往效力。此項裁判，尤其有待商榷。

Liability for non-conforming performance and for warranty is a very important issue both in theory and in practice. In order to solve the problems of the concurrent relationship between the liability for non-conforming performance and the liability for warranty for defective goods and works, the Supreme Court has delivered two resolutions in 1988 and 2007 respectively. After the resolution of 1988, it remains questionable whether the doctrine of the liability for non-conforming performance is applicable to the case in which the delivered goods contain defect that exists prior to the conclusion of the contract of sale. According to the research of this paper, the answer to the above question should be a positive one. As to the issue of the concurrent relationship between non-conforming performance and warranty for defective works in the case of contract of hire to work, the research of this paper demonstrates that the Supreme Court’s resolution of 2007 will definitely result in the difficulty in istinguishing defective damages (damages caused to the defective work itself) and consequential damages (damages arose from the defective work and caused to the property other than the defective work or to the integrity interest of the owner of the work).