Acute rhinosinusitis (ARS) is frequent in children. Patients with allergic rhinitis show signs of more impaired paranasal sinus functioning than normal subjects during viral colds. This study evaluated the effectiveness of administering antibiotics alone to treat ARS in both allergic and non-allergic children. We obtained informed consent from the parents of each patient enrolled in the study. 97 children, 55 males and 42 females aged between 4 and 9 years (46 of whom were allergic), suffering from ARS, were treated with amoxicilline-clavulanate (50 mg/Kg bid) for 14 days. Symptoms and endoscopic signs of illness were evaluated at baseline and immediately after treatment. Symptoms improved significantly (p<0.001) after treatment in 84 patients, equally distributed between allergic and non-allergic subjects. On the contrary, endoscopic signs disappeared only in 49 children, 9 of whom were allergic (OR 14.9, 95%CI 4.6-40.1, p<0.001). Slight to fair agreement was observed between clinical symptoms and endoscopic signs (agreement 64% , Kappa=0.28, McNemar test p<0.001). Antibiotic therapy alone in the treatment of ARS may be generally insufficient to resolve symptoms, mainly endoscopic signs. Moreover, in allergic children this issue appears to be more evident.