本研究探討製造商在面對一般購買者與禮物購買者兩種不同類型消費者下最適的產品線設計。一般購買者購買產品目的是源自於自身的需求，而禮物購買者是源自於他人的需求。本文在假設禮物購買者不清楚受贈者的偏好，且終端消費者對品質的邊際效用不同下，發現禮物購買者的出現製造商將不會以最高品質的產品項目服務禮物購買者，但可能以完整的禮品產品線、或以單一禮品產品項目服務全部禮物購買者或可能引導禮物購買者購買正規產品項目作為禮物。此外，禮物購買者的出現將影響製造商用以服務一般購買者的產品線設計與最適定價，且進而影響一般購買者的福利。另一方面，本研究的延伸模型考量存在部分禮物購買者十分在意禮物的品質是否符合受贈者預期且為無窮風險趨避的情況，結果發現，隨著無窮風險趨避禮物購買者人口的增加，製造商愈有可能專注於以相同的高端產品項目服務一般高端購買者與無窮風險趨避禮物購買者。

This paper considers the optimal design of a product line for a manufacturer that faces gift buyers who make purchases for other consumers' consumption, and regular buyers who make purchases for their own consumption. Assuming that a gift buyer has imperfect knowledge about the gift receiver's preference and end users differ in their valuations to quality, we show that in the presence of gift buyers, (i) the manufacturer will not serve the gift buyers with the highest-quality product item; (ii) the manufacturer may offer a full line of gift items, may serve all gift buyers with one single gift item, or may simply induce gift buyers to buy regular products as gifts; (iii) the presence of gift buyers affects the manufacturer's optimal pricing and product-line decisions, which in turn affects the regular buyers' welfare. In an extended model of the paper, we also consider the case where there exist some gift buyers who are very concerned about whether the quality of gifts meets receivers' expectation and are infinitely risk averse. We find that in this case the increase in the population of infinitely risk averse makes it more likely that the firm focuses on the high-end regular buyers and the infinitely risk averse gift buyers by offering them the same high-end product.