Background: Asthma is a common chronic inflammatory disease of the airways in which genetic factors play a major role in its pathogenesis. High serotonin serum levels in patients with asthma suggest that serotonin is involved in the pathophysiology of the disease. Serotonin clearance is mediated by the serotonin reuptake transporter, and functional polymorphisms in this gene lead to altered serotonin reuptake efficiency. Objective: The aim of this study was to investigate the relationship between serotonin transporter gene polymorphisms and asthma. Methods: Serotonin transporter gene polymorphisms (5-HTTLPR, rs35521 and STin2.VNTR) were assessed by PCR-based methods in 100 children with mild to moderate persistent asthma and compared with 100 healthy controls. Results: There were no significant differences in allele, genotype or haplotype frequencies between patients and controls. No association was observed between SERT gene polymorphisms after stratification of patients for sex, age, spirometry indices, family history, passive smoking behavior and concomitant allergic rhinitis. Significant differences were observed in the distribution of 5-HTTLPR alleles (p = 0.025) and genotypes (p = 0.021) between patients with and without atopic dermatitis. Conclusions: Despite strong evidence suggesting the role of serotonin in the pathophysiology of asthma, we found no association between serotonin transporter gene polymorphisms and mild to moderate persistent asthma. Further serotonin transporter gene analyses in patients with severe asthma may open up new horizons in the utilization of common serotonin regulators to treat asthma, based on their pharmacogenetic effects. However, serotonin may also be indirectly influenced by emotional stress during asthma attacks.