The rapid development of multimedia applications and the Internet leads to the demand of mobility for these services. New wireless standards are supporting high data rates and additional services, but they require complex realizations in both frontend and baseband of a mobile system. The obtainable performance of such a system is often limited by the power consumption of the implementation, as long stand-by and talk times are still key parameters of a mobile terminal. Also the thermal problem, given by insufficient heat removal with highly integrated high-performance circuits in narrow-spaced terminals, calls for optimizations concerning power consumption. This paper discusses the problem of power consumption in system on chip (SoC) design for mobile applications and presents methodologies for power optimized design.