Methods used to select opinion leaders for informal behavior change interventions vary, affecting the role they adopt and the outcomes of interventions. The development of successful identification methods requires evidence that these methods achieve their aims. This study explored whether the “whole community” nomination process used in the ASSIST smoking prevention program successfully identified “peer supporters” who were well placed within their school social networks to diffuse an antismoking message to their peers. Data were collected in the United Kingdom during A Stop Smoking in Schools Trial. Behavioral data were provided at baseline and post intervention by all students. Social network data were provided post intervention by students in four control and six intervention schools. Centrality measures calculated using UCINET demonstrate that the ASSIST nomination process successfully identified peer supporters who were more socially connected than others in their year and who had social connections across the entire year group including the program’s target group. The results indicate that three simple questions can identify individuals who are held in high esteem by their year group and who also have the interpersonal networks required of opinion leaders to successfully disseminate smoke-free messages through their social networks. This approach could be used in other informal health promotion initiatives. Adolescent smoking remains an issue of global public health concern. The 2009/2010 Health Behaviour in School-Aged Children (HBSC) survey (Currie et al.,) noted that 6% of 13-year-olds were weekly smokers. In Wales, UK, 22% of girls and 18% of boys aged 15 years reported having first used a cigarette at age 13 or younger, and 6% girls and 3% boys aged 13 smoke at least once a week. In the United States these figures are lower: 11% of girls and 14% of boys aged 15 years have smoked by age 13, and 3% of girls and 4% of boys aged 13 smoke at least once a week. A number of risk factors, including peers, family factors, school factors, socioeconomic status, ethnicity, depression, and stress, have been identified as instrumental in adolescent smoking (Conrad, Flay, & Hill, 1992; Schepis & Rao, 2005; Tyas & Pederson, 1998), although these may operate differently in different social, cultural, and legislative contexts. For example, educational systems differ across the world, exposing young people to different social and environmental influences within this setting. Furthermore, the introduction of tobacco-related legislation and the implementation of education and prevention interventions has not been uniform worldwide.