本文建立一理論模型探討本國廠商面臨外國廠商之競爭時，是否採取仿冒。研究結果指出仿冒不必然是本國廠商的最適決策。在自由貿易下，本國廠商採取仿冒可賺取較多利潤。然而，在政府採行關稅保護下，若外國產品品質相對低，則本國廠商將採創新；反之，若外國產品品質相對高，則本國廠商將從事仿冒行為。

This paper presents a model of vertical differentiation to anaalyze a domestic firm's counterfeiting behavior in the existence of network effect. We find that the domestic firm's optimal counterfeiting behavior depends on the foreign product's quality as well as the government's trade policy. Even in the absence of law enforcement, free-riding a pioneering product's great reputation is not necessarily profitable. Under protectionism, if the foreign product's quality is relatively low, then the domestic firm tends to be an innovator; otherwise, it tends to be a counterfeiter. This result could explain why the quality of a counterfeit product is often far behind that of a legitimate one as stated in the U.S. House of Representatives Committee on Energy and Commerce (1985). On the other hand, in the case of free trade, counterfeiting is always profitable for a domestic firm.