Children have air-filled paranasal sinuses from birth. Acute sinusitis is common in early childhood and complicates 5-13% of common colds. Bacteriology comprises 30% Streptococcus pneumoniae, 20% Haemophilus influenzae, 20% Moraxella catarrhalis. While suppurative complications are rare, there has been an increasing focus on comorbidity affecting the lower airways (asthma). The diagnosis is based on clinical criteria developed through microbiological studies. Antibiotic treatment is controversial, but evidence suggests an effect when the diagnosis has been made correctly. We advocate antibiotic treatment in selected cases.