Allergic rhinitis (AR) and asthma are closely associated in children. Reduced FEF25%-75% which reflects small airway airflow limitation is frequently observed in asthma. This study aimed to examine the proportion of small airway dysfunction in children with AR and to determine its associated factors.Methods: The medical records of 144 aged 6-18-year children with AR without overt asthmatic symptoms were retrospectively reviewed. Subjects were divided into 2 groups according to the FEF25%-75% values; normal FEF25%-75% group (n = 129) and reduced FEF25%-75% group (n = 15). Clinical data, allergen sensitization profile, exhaled nitric oxide, spirometry, and methacholine provocation test results were compared between the two groups.Results: The mean FEV1 and FEF25%-75% values in the reduced FEF25%-75% group (73.5 ± 9.4%pred and 56.0 ± 7.7%pred, respectively) were significantly lower than in the normal FEF25%-75% group (87.0 ± 12.5%pred and 99.1 ± 21.4%pred, respectively). The mean disease duration was significantly longer in the reduced FEF25%-75% group than in the normal FEF25%-75% group (5.39 ± 1.85 y vs 3.14 ± 1.80 y, p < 0.001). Subjects with positive bronchial hyperresponsiveness (MChPC20<16 mg/mL) were more frequently detected in the reduced FEF25%-75% group than in the normal FEF25%-75% group (26.7% vs 8.52%, p = 0.013). Long disease duration and severity of AR were significantly associated with impaired FEF25%-75% values.Conclusions: Subjects with AR alone may have impaired FEF25%-75% values which is considered as a marker of early bronchial involvement. Longer disease duration and severity of AR are important risk factors for progressive declines in small airway function. Physicians should be aware of need for the measurement of FEF25%-75% values for early detection of small airway dysfunction, particularly in children with severe long-lasting allergic rhinitis.