The purpose of this paper is to forecast possible diffusion patterns of the next generation mobile telecommunications services - WiBro, HSDPA, SDMB, TDMBbased on the critical diffusion factors and econometric analysis of diffusion patterns of Korean telecommunications market. The Bass model is used for analyzing patterns of diffusion, which is used as supporting theory of cluster analysis of diffusion patterns. In addition, critical factors affecting diffusion are derived from successful diffusion cases and diffusion failure cases. Critical diffusion factors are utilized as a basis for making expert survey questions for evaluating new mobile telecom services. The results of experts`` evaluation on new services are categorized for diffusion types of cluster analysis. HSDPA is expected to achieve fast diffusion according to the timing of introducing mobile VoIP and 4G, or it is supposed to follow innovative coefficient oriented pattern. WiBro is thought to be influenced by imitative factors. SDMB has advantages in innovative factor, and disadvantages in cost and marketing capability. Thus, it is expected to present diffusion with high innovative coefficient. Competitiveness of TDMB in imitative factors leads patterns controlled by imitative power. Also, it is expected to follow fast diffusion with securing technology and service quality.