We genotyped CTLA4 CT60 (rs3087243) functional single nucleotide polymorphism (SNP) in children with asthma and in healthy controls and correlated the genotype data with asthma clinical data, including treatment response with inhaled corticosteroids measured by forced expiratory volume in the first second (FEV(1)). FEV(1) increased by 21.7% after 4 weeks of therapy in atopic asthmatics with the A/A genotype compared with an 8.6% increase in heterozygotes and a 5.8% increase in G/G homozygotes (p <0.01). Genotype and allele frequencies in asthmatics did not differ significantly from those in the control group. SNP CT60 in the CTLA4 gene is significantly associated with the response to treatment with inhaled corticosteroids in children with atopic asthma and could be a useful biomarker for personalized therapy in asthmatic children. SNP CT60 in the CTLA4 gene plays only a minor role in genetic susceptibility to childhood asthma in the Caucasian population.