HYPOTHESIS AND BACKGROUND: Passive smoking in the paediatric age group is associated with an increased frequency of a number of childhood respiratory disorders. However, its effect on ciliary regeneration after functional endoscopic sinus surgery for chronic sinusitis has not previously been reported. MATERIAL AND METHODS: We conducted a prospective, nonrandomised cohort study on 38 paediatric patients with chronic sinusitis. We compared two patient groups--passive smokers and those not subjected to passive smoking--as regards ciliary regeneration after functional endoscopic sinus surgery, using objective methodology. RESULTS AND CONCLUSION: We found passive smoking to have a negative impact on sinus cilia regeneration following functional endoscopic sinus surgery.