Misclassification errors in a dependent variable can introduce attenuation bias to covariate effects in a binary choice model. Misreporting of smoking behaviours by adolescents has been widely documented. However, the consequence in empirical studies of adolescent smoking participation has received little attention. This study uses the Health Survey for England (HSE) to investigate the extent and implication of misclassification errors in self-reported smoking among adolescents aged 11–15 years.