Consumer needs becomes various in a mature mobile telecommunication market, while service differentiation is hard to achieve. Because of the introduction of number portability, switching barrier becomes lower and the competition among telecommunication service providers is getting fierce in order to maintain and obtain customers. Moreover, HSDPA, which is a new telecommunication service, caused the intense marketing activity for the move to the next generation customers. Under these circumstances, brand equity can be a key to a long-term competitive edge for mobile phone service providers. However, there were few researches reporting the mobile telecommunication brand equity, and none of them analyzed if customer equity which particularly is developed at the CDMA market has an effect on HSDPA service. In this study, we identified the determinants of mobile telecommunication brand equity, which is focused on brand image, customer benefit, price, service quality, and marketing activity, and its influence on the HSDPA service subscription behavior. Finally, we suggested the strategic implication of brand management strategies for mobile phone service providers.