Introduction: Infants with atopic dermatitis (AD) is at risk of later development of asthma that is associated with risk factors such as severity, early onset, persistence, egg or house dust mite sensitization, and filaggrin gene mutations. Impulse oscillometry (IOS) is a useful tool to assess airway obstruction in asthma. The purpose of this study was to evaluate the association between lung function at 3 years and risk factors for asthma development in children with infantile AD. Methods: We enrolled infants and young children who developed AD before the age of 2 years, and analyzed 144 patients who completed follow-up by the age 3 years. The median (interquartile range, IQR) age was 39 (37-42) months and 64 (44.4%) patients were female. Clinical information including SCOring of Atopic Dermatitis (SCORAD) score was obtained at each visit. Serum specific IgE against egg white, cow’s milk and peanut were measured at least once a year. Skin prick test was performed at 3 years of age, when resistance (R5) and reactance (X5) at 5 Hz were measured using IOS. The data underwent the Spearman correlation analysis, as well as comparative analyses using the Mann-Whitney U test. Results: The median (interquartile range) values of R5, X5 and X5 differences between predict and best were 1.23 (1.05-1.43) kPa·L-1· s-1, -0.29 (-0.39-[-0.19]) kPa·L-1· s-1 and 0.07 (-0.03-[0.16]) kPa·L-1· s-1, respectively. X5 was negatively correlated with AD severity at 3 years, while R5 did not show statistical significance. Sensitization to food allergens were not associated with R5 or X5. When compared between children with inhalant allergen sensitization and non-sensitization, R5, resonance frequency and area of reactance were not significantly different. However, the median of X5 differences between predict and best in children with inhalant allergen sensitization was significantly lower than those without sensitization (0.04 vs 0.09, P=0.047) Conclusions: Inhalant allergen sensitization and severity of AD are associated with the decrease in peripheral airway reactance at 3 years. These findings suggest that IOS at 3 years might be used for predicting later development of asthma in children with infantile AD. Further studies with long-term follow-up are needed.