Sinusitis is a common disease among children. Acute bacterial sinusitis usually develops after viral upper respiratory tract infection. Acute bacterial sinusitis diagnosis in children is generally based on clinical criteria (the situation whereby the findings and symptoms of upper respiratory tract infection are more severe or last longer than expected in a viral upper respiratory tract infection). Because the treatment of acute bacterial sinusitis requires the use of antibiotics, correct diagnosis is crucial. This article reviews sinusitis pathogenesis, classification of sinusitis, the pathogens that cause sinusitis among children - primarily including acute bacterial sinusitis-, clinical findings of sinusitis and current knowledge about the diagnosis and treatment of sinusitis.