With mobile operators having a large customer base and E-Payments getting popular, there is a shift of focus on the huge potential that M-Commerce market offers. Mobile payment service is the core for the success of M-commerce. Mobile payments allow customers to buy digital goods from anywhere and anytime using Internet and mobile environments. Ubiquity, reachability, localization, personalization and dissemination of information are the characteristics that favour mobile payments and encourage the consumers and merchants to use them. This chapter examines various aspects of mobile payments like architectures, limitations, security and trust issues. It also discusses and compares the existing payment procedures of several different companies providing mobile payment services. While exploring the advantages of shifting to mobile payments, the problems that have to be dealt with when adopting new solutions are discussed. Finally the chapter concludes by identifying a common set of requirements criteria for successful global mobile payments.