목적: It is well known that allergic rhinitis as a risk factor for adenotonsillectomy. However, the symptom improvement after adenotonsillectomy in the presence or absence of allergic rhinitis is not well documented. Hence, we aimed to compare the symptom improvement after adenotonsillectomy between atopic or nonatopic patients. 방법:A retrospective analysis was performed younger than 10 years old patients who received adenotonsillectomy. All patients underwent skin prick test or MAST before surgery and questionnaire including symptoms and SNOT-20 was performed before, 1 week and 1 year after surgery. 결과:Among 250 patients, allergic group was 131 and non-allergic group was 119, showing higher prevalence of allergic patients among adenotonsillectomized patients. Both groups showed dramatic improvement of symptoms such as snoring and mouth breathing. However, allergic group showed less improvement than non allergic group in snoring(allergic7.85->3.93 non-allergic6.08->1.15,p<0.05)and mouth breathing (allergic7.02->5.93 non-allergic7.47->2.51, p<0.05 ). Nasal symptoms such as nasal obstruction also showed a similar pattern(allergic8.53->4.58 non-allergic6.35->1.38,p<0.05). Multivariate analysis showed that preoperative mouth breathing was dependent on tonsil size (p<0.001, R2=0.154) and postoperative mouth breathing was dependent on presence of allergic rhinitis (p<0.001, R2=0.420) Preoperative and postoperative nasal symptoms such as nasal obstruction was dependent mainly on presence of allergic rhinitis rather than tonsil size (p<0.001, R2=0.614). These suggest the importance of allergic rhinitis as a risk factor for mouth breathing and nasal obstruction. 결론:Allergic rhinitis is a risk factor for adenotonsillectomy and not only allergic symptoms but also obstructive symptoms such as snoring and mouth breathing improved less in allergic group than non-allergic group. Hence, allergic patients should be monitored for long-term basis and more carefully after adenotonsillectomy.