Ever since the Telecommunications Act of 1996, there has been increasing concentration in the US cellular market. Baby bells have merged with one another, until only two dominant cellular carriers, AT&T and Verizon, are left in the market. The other two legacies, Sprint and T-Mobile, have survived AT&T’s monopoly, and provided most cellular services. The market has become an oligopoly. Almost every proposed merger had been approved until recently the merger between AT&T and T-Mobile was rejected by the FCC and DOJ. The primary factor in shaping the market structure is regulation.Researchers have long focused on the role of legislation in shaping the market. This paper xamines the mobile market structure from a different market perspective: mobile devices. Since the oligopoly was formed, the Big 4 have been competing on mobile devices, not on prices, services or networks. Mobile devices have played an essential part in tilting the playing field. They and cellular networks are complementary goods. AT&T improved its runner-up position by signing an exclusive contract with Apple and monopolizing the iPhone market for four years. On April 12, the last of the Big 4, T-Mobile, will offer iPhones and introduce aggressive rate plans in order to break the deadlock. Since they are major factors in structuring the U.S. market, mobile devices cannot be overlooked.In China, the market structure is in some ways similar. There are the Big 3: China Mobile, China Telecom, and China Unicom. However, the situation is totally different. The majority of mobile devices are unlocked, although the Big 3 offer them with contracts as well. The cellular networks are 3G. To make things more complicated, the Chinese government ordered each carrier to apply a different 3G standard. China Mobile has been assigned TDS-CDMA, China Telecom CDMA2000, and China Unicom WCDMA. The three standards are non-compatible, which results in non-compatible devices. This situation requires that the Big 3 compete on prices and network quality more fiercely than the Big 4 in the US.This paper examines the history of market share changes in light of the release of popular mobile devices in both the US and China cellular markets, and compares the influences of the devices on the two markets. Reasons for the similarities and differences are proposed. The CPE market has been left unregulated by the FCC, which can be an important factor in boosting or stifling competition in the cellular market. Recommendations are made to both regulators and researchers that the mobile device market should receive more attention, and in some cases, government involvement may be necessary to assure a level playing field and competition.