Acute rhinosinusitis is a common entity in children, most are due to viral infections, however up to over 80% children with rhinosinusitis are prescribed with antibiotics. Acute bacterial sinusitis should be diagnosed in when a child has 1) a severe onset with a fever over 39℃, purulent nasal discharge or facial pain for 3 to 4 days; 2) persistent illness with rhinorrhea, daytime cough or both for over 10 days with no clinical improvement; or 3) worsening course with symptoms aggravating or new onset symptoms including fever, headache, cough or rhinorrhea after clinical improvement. Radiographic imaging is not recommended for differentiation of viral and bacterial rhinosinusitis, however a contrast-enhanced computed tomography or magnetic resonance imaging may be done in cases with orbital or central nervous system complications. Antibiotics may be prescribed in cases with severe onset or worsening course. Antibiotics may be prescribed after additional observation for 3 days in children with persistent illness. Amoxicillin-clavulanate (amoxicillin 40 to 50 mg/kg/day, every 12 hours) is recommended for initial treatment and high dose amoxicillin-clavulanate (amoxicillin 90 mg/kg/day every 12 hours) may be considered in cases with severe infection, children in day care center, under 2 years of age, recent admission history, previous antibiotics within 1 month and immunocompromised children. Clinical response should be reassessed in cases of worsening or failure to improve within 72 hours of treatment.