This study presents a model integrating research on mobile social network services (SNS) and word-of-mouth (WOM) by examining the sustainable diffusion of fashion information via multidimensional effect factors, including the social relationship and sub-network structure characteristics of SNS. Implications for expanded research scope and methods are generated by applying social network analysis to information diffusion on friends-based SNS for sustainable development, which is connected to the social cascade phenomenon. This study investigates the relationship between the social network characteristics of subscribers and the sub-network structure characteristics of friends-based SNS and examines the effect of sub-network structure characteristics on fad-like behavior and WOM. We examine 311 people with experience in fashion information activities using friends-based SNS services for data analysis and perform frequency analysis, reliability and validity analysis, measurement model analysis, and path analysis using SPSS 20.0 and AMOS 20.0. This study furthers our theoretical and practical understanding of the network extension pattern in fashion information diffusion in mobile friends-based SNS. The study also points out the need for community network management and identifies the key factors in friends-based SNS, thus providing strategic guidelines for spreading fashion information effectively.