Social network marketing refers to a set of marketing activities that exploit social relationships between consumers to increase sales. There are different types of marketing using social networks such as word-of-mouth marketing, diffusion of innovation, buzz marketing and viral marketing [1]. Among these network-based marketing examples, word-of-mouth marketing has more credibility [2], because there is no direct connection between the sender and the merchant. Accordingly, the information is considered independent and subjective. In recent years, many researches in word-of-mouth marketing investigate the discovery of influential nodes in a social network. These influential people are called opinion leaders in literature. Organizations interested in e-commerce need to identify opinion leaders among their customers, as well as the location (website) where they go online. This is the place where they can market their product.1.1. Social Network Analysis Regarding the importance of interpersonal relationship, studies are looking for a formal method to measure "who talks to whom" in a community. These methods are known as social network analysis [3, 4, 5, 6]. Social network analysis includes the study of interpersonal relationships. It is usually more focused on the network itself, rather than the characteristics of the members [2]. Valente and Rogers [7], described social network analysis from the perspective of interpersonal communication as “formal methods for measuring who talks to whom within a community”. Social network analysis allows researchers to identify the people who are most central in the network and therefore most influential. By using these central people or opinion leaders as seeds of diffusion of... middle of paper... leaders and employing social networks to improve marketing response, you get. In Section 2, the concept of opinion leadership is discussed and the different titles (opinion leaders, influential people, market experts and key players) that have been introduced by different studies to refer to the influential group in social networks. So, regarding the similarity of these titles on the concept and common identifying factors, considering all the definitions and characteristics proposed for opinion leaders, influential people, market experts and key players, three comprehensive classifications are proposed which include structural characteristics, relational and personal. In section three, the methods of identification and selection of opinion leaders are examined, and the appropriate parameters for the analysis of these methods are extracted and shown in a comprehensive diagram.