North Korea and Iran have been featured in all official U.S. missile defense policy documents since the late 1990s. The threat posed by two countries to the United States and their allies’ armed forces deployed in various regions has been the main incentive for the development of regional missile defense (theater missile defense) programs for more than 20 years. All this time, there has been an ongoing debate among American politicians, strategists, and academic experts on the prospects and specifics of the regional missile defense architectures, levels of U.S. allies’ participation in their development, as well as the very need to deploy these systems in North-East Asia, the Middle East, and Europe. The paper attempts to summarize and analyze the arguments of both the proponents and opponents of the idea to use the regional missile defense systems in the regional deterrence of North Korea and Iran.The first section examines approaches of different U.S. administrations to this issue. The author emphasizes that the Biden administration officials have already confirmed most of the basic postulates formulated by the Trump administration on the matter. According to them, the high efficiency of regional missile defense facilitates regional deterrence of the DPRK and Iran.The second section examines debates in the U.S. expert community. The author identifies two main approaches. The first basically repeats the arguments of the U.S. administration on the benefits of regional missile defense for regional stability. According to the second approach, the regional missile defense may destabilize the situation in the region without enhancing the protection of the U.S. and their allies’ armed forces.The third section provides a critical analysis of the debate. The author concludes that the arguments and assessments of both the opponents and proponents of the deterrence of the DPRK and Iran by means of regional missile defense are theoretically ill-founded and often one-sided. Subsequently, many crucial issues related to the use of missile defense systems and their potential impact on the regional security remain understudied. All this suggests that there is a need for a more detailed study of this issue, particularly given increasing regional tensions.