The purpose of this study was to assess the perceptions of Thailand adolescents regarding the prevalence of smoking, the popularity of smoking among successful/elite elements of society, and disapproval of smoking by friends and parents. These perceptions were analyzed in conjunction with actual smoking and smoking susceptibility rates among the subjects to determine whether beliefs and behaviors were associated with each other. This study was conducted among a school-based sample of 2516 Chiang Mai, Thailand upper secondary and vocational students. Although perceived prevalence of smoking was not associated with smoking outcomes, perceived popularity of smoking among the successful and elite was associated with higher risk, and perceived disapproval by friends/parents was associated with lower risk. Youth smoking programs should consider assessing and taking these social normative factors into account when considering educational intervention strategies that aim to lower adolescent smoking rates. (Contains 5 tables.)