本文從廠商間以比較廣告來影響消費者偏好，進而利用價格競爭追求利潤的角度，分析廠商在比較廣告策略上若是採取不合作競爭或採取合作的聯合行為，對廠商的比較廣告，產品價格以及利潤水準，消費者剩餘，以及社會福利水準之影響。我們發現廠商只有在特定忠誠度區隔下，從事比較廣告才會有助於其市場佔有率以及利潤水準。這隱含在特定的忠誠度區隔下，廠商利用比較廣告提高產品差異化以增加其市場佔有率後，廠商之間的價格競爭反而會減弱。我們獲得消費者忠誠度的變動對社會福利的影響效果需視消費者所處的忠誠度區隔而定。當消費者的忠誠度區隔若是處於相對高的情況下，廠商從事合作的聯合廣告策略可提高社會福利。

This paper investigates those cases where firms use both comparison advertising to affect the preference of consumers and price competition to acquire greater profits, and then we analyze the effects of firms’ noncooperative and cooperative comparison advertising strategies on those firms' comparison advertising, product prices and profits, consumer surplus and social welfare. We find that only with specific loyalty segmentation, can firms increase their market share and profits by using comparison advertising. However, this implies that with specific loyalty segmentation, firms engaging in comparison advertising to intensify product differentiation in an effort to increase their market share actually tend to loose the intensity of price competition. Finally, we find that the effects of changing consumers’ loyalty segmentation on social welfare depend on which interval those consumers belong to. When consumers have a relatively high degree of loyalty, firms employing cooperative comparison advertising can actually increase social welfare.