Adenoid hypertrophy is the most common cause of upper airway obstruction and sleep-disordered breathing in children, yet its pathogenesis remains unclear. The identification of the novel helper T cell subsets, Th17 cells and regulatory T cells (Tregs) could provide new insight into our understanding of the mechanisms involved in the development of this condition. The purpose of this study is to evaluate the adenoidal lymphocyte subsets to describe the percentage of various lymphocyte subsets in hypertrophied adenoids and correlate them with symptom severity. Twenty consecutive children undergoing adenoidectomy were included, and lymphocytes were isolated from their adenoids. T cell subpopulations were detected by flow cytometry using a fluoresceinated monoclonal antibody directed against a number of cell markers (CD4+, CD8+, CD25+, FOXP3 IL17+, and others). We found a significant negative linear correlation between the Th17/Treg ratio and the patients' clinical scores (R = -0.71 p < 0.005). The correlation was independent of age and gender. Decreased ratios of Th17/Treg subpopulations may play a role in the pathogenesis of adenoid hypertrophy.