A citation-based method of estimating the life span of a patented technology is proposed In this study. The suggested framework Includes : (1) estimation of citation frequency of an individual patent within a technology group. (2) calculation of a mutual citation frequency between citing patent and cited patents, (3) calculation of the period for cited patents from the year of registration to the year of being cited most recently and (4) description for technology group using descriptive statistics such as mean, median, mode, etc. The framework suggested in this study was applied to the US patent data between 1976 and 2004 for 5 communications areas.