Many studies have suggested that brain-derived neurotrophic factor (BDNF) is involved in the reward system of addiction, and that nicotine may induce alterations in BDNF gene expression and its protein level within the mesocorticolimbic system. We investigated the BDNF levels and biochemical-hematological parameters of smoker and non-smoker groups, and examined the association of the Val66Met BDNF gene polymorphism with BDNF serum levels and cigarette smoking. The study sample comprised 311 Thai volunteers (200 smokers; 111 non-smokers). The levels of serum BDNF and biochemical-hematological parameters were determined. The Val66Met BDNF polymorphism was genotyped by the polymerase chain reaction-restriction fragment length polymorphism technique.