贈品促銷在各行各業的採用愈來愈普遍，但有關贈品促銷的影響效果卻被許多學者所忽略，原因可能是因為大部分學者將贈品價格愈高，促銷效果愈好的正向影響效果視為理所當然，但是否真實如此?本研究認為若探討贈品促銷的效果，其中所探討的贈品促銷是指買A送B，其中A與B為不同產品類別。而針對贈品價值的吸引力方面，應著眼於贈品價格相當於主產品價格的百分比來進行探討，在本文中簡稱為贈品促銷深度(例如，贈品促銷廣告中：「購買一雙$2000的Nike球鞋，即贈送價值$200的Casio手錶一只」，則此贈品促銷深度為$200/$1000=10%)。本文將贈品促銷深度分為十組(10%、20%...100%)，並加入主產品與贈品品牌形象的干擾變數一同探討。正式研究包含三項研究主題，深入分析贈品促銷深度的轉折現象、對產品知覺價值影響效果與外溢效果。理論基礎採用內在參考價格相關理論與定錨調整鋰論，研究方法採用10x2x2的組間因子設計之實驗法進行，針對北部兩所大學在校學生進行問卷發放，有效問卷975份。 研究主題一的目的欲找出贈品促銷深度對贈品價格合理性影響的轉折點，研究結果顯示，當主要產品與贈品沒有出現品牌訊息時，贈品促銷深度的轉折點為50%，但加入品牌訊息之後，轉折點便有所不同，品牌形象高時，贈品促銷深度轉折點為50%，品牌形象低時，轉折點往下修正，變成40%或20%。 根據研究主題一找出的轉折點，研究主題二則進一步探討轉折前的合理贈品促銷深度以及轉折後的誇張贈品促銷深度對產品知覺價值的影響效果，再加入主產品與贈品的品牌形象之情境變數，探討此三者彼此間的互動如何影響消費者對贈品促銷的評價。研究結果發現：(1)合理深度下，深度愈深，整組產品知覺價值愈高，但誇張深度下，深度愈深，整組產品知覺價值愈低。(2)贈品促銷深度愈深，贈品價格知覺愈高;合理深度愈深，贈品價值升值愈少，誇張深度愈深，贈品價值貶值愈多。(3)主產品與贈品品牌形象皆產生干擾效果。 研究主題三則想瞭解消費者心中對贈品免費的印象是否會外溢出去影響到贈品同類產品的其他品牌(同品他牌)、或者外溢出去影響到贈品同品牌的其他產品(同牌他品)，而貶低對同品他牌或同牌他品的評價? 研究結果發現：贈品促銷的確會產生外溢效果，且隨著合理深度加深，外溢效果降低，但隨著誇張深度加深，外溢效果增加。透過本研究，一方面可更豐富贈品促銷效果的相關學術研究結果，另一方面可提供實務界相關建議。 / Gift promotion is taken as a common technique in most industry for a long time. It is believed that the higher the gift price is, the more successful gift promotion works. But, must it be true? In this study, gift promotion was defined as “buy A, get a free gift B”；that is, A and B were different products. Furthermore, promotion depth was taken as a main independent variable and defined as a percentage of gift price by main product price. By experiment design, promotion depth was manipulated as ten groups (10%, 20%,..., 100%), and brand images of main product and gift were chosen to be two moderators in this study. An 10x2x2 between subject design was further held, and totally 975 valid questionnaires was gathered. Three themes were arranged to further investigate effects of gift promotion. Inferences and discussions were based on literature of reference price and anchor-adjustment theory. In the first research theme, it is proposed that there is a turning point in promotion depth—50% of promotion depth, and the turning point was fluctuant in accordance with brand image. If the brand image was high, the turning point was 50%；however, if the brand image was low, the turning point was downward to 40% under low brand image of main product and downward to 20% under low brand image of gift. Based on these findings, promotion depth was divided into two categories—reasonable (depth before turning point) and exaggerated (depth after turning point) promotion depth—in order to do further investigations. The second research theme focused on the effect of reasonable or exaggerated promotion depth and its interaction with brand image of main product and gift. Findings were (a) In the range of reasonable promotion depth, the deeper the promotion depth was, the higher the perceived value of product bundle was (eg. positive relationship). However, in the range of exaggerated promotion depth, negative relationship was exhibited. (b) The deeper the promotion depth was, the higher the price perception of gift was. In the range of reasonable promotion depth, as the depth increased, value-adding level of gift decreased. In the range of exaggerated promotion depth, as the depth increased, value-discounting level of gift increased. (c) The brand image of main product and gift did show significant moderating effect. The third research theme was going to investigate whether the discounting perception toward gift would spill to other products with the same brand of the gift, or spill to the same product with other brand. In this study, we defined the phenomenon as a “spillover effect” of gift promotion. Findings were: (a) No matter in the range of reasonable or exaggerated promotion depth, gift promotion did cause discounting of perceived value toward other products with the same brand of the gift and to the same product with other brand. That is, spillover effect did exist. (b) As the promotion depth increased, the spillover effect would first go downward then upward. In other words, the relationship between promotion depth and spillover effect showed a type of U-shape. Findings of this study will enrich literature of promotion as well as offer practical suggestions to managers implementing strategies of gift promotions.