Background: Glucocorticoids (GCs) represent the mainstay therapy for asthmatics. A subset of severe asthmatics fails to respond to steroid-based therapies, leading to important healthcare costs. Single nucleotide polymorphisms (SNPs) of glucocorticoid receptor genes were associated with a response to GC. We evaluate the possible relation of BclI and A3669G SNPs to clinical, biological and functional characteristics of asthmatics. Methods: We recruited 172 mild-to-severe asthmatic outpatients referring to the Severe Asthma and Rare Lung Disease Unit at San Luigi University Hospital. Clinical data were obtained at recruitment when spirometry tests and peripheral blood sampling were performed. Patients were genotyped for BclI and A3669G through the pyrosequencing assay results. Results: Patients with the A3669G AG genotype were younger, allergic and had higher IgE levels compared to AA genotype (p < 0.05). Moreover, asthmatics with the AA genotype had a lower post-bronchodilator FEV1/FVC ratio than the GG genotype (p < 0.05), and a higher RV/TLC ratio than the AG genotype (p < 0.05). Conclusions: The A3669G AG genotype might be related to type-2 allergic asthma; in particular, allele A of A3669G SNP was associated with GC response in our asthmatics. In conclusion, this observational cross-sectional study suggests a possible role of A3669G SNP as a predictor of asthma severity and phenotype.