This article describes, based on the fundamentals of GSM radio network planning, the process of planning and optimizing UMTS networks. It highlights the key differences to existing 2G technologies and explains why UMTS radio network optimization is so complex that it cannot be done manually any more. This article gives some examples of cost efficient UMTS radio network enhancements in order to maximize future network capacities. It explains how UMTS return on investment is influenced by using advanced methods for radio network planning and optimization.