“…Some studies classifying smokers by the stages of change have also used different biomarkers of tobacco consumption to validate selfreported consumption (de Granda-Orive et al, 2004;Prochaska and DiClemente, 1983), but few of them have related biomarkers to different smoker characteristics (Ahijevych and Parsley, 1999;Etter et al, 2000). Cotinine, the major metabolite of nicotine, can be related to nicotine dependence; thus, baseline cotinine levels may be useful for categorising smokers that enter smoking cessation programmes (Hall et al, 1984;Paoletti et al, 1996;Tønnesen et al, 1993).…”