Previous studies have shown that sleep complaints are common in adult patients with cystic fibrosis (CF). However, there is very little data on sleep in children and adolescents with CF and the association with severity of lung disease. A prospective study was conducted in CF children and age-matched controls. All patients completed sleep questionnaire and underwent an overnight polysomnographic study. Thirty-eight children and adolescents met the criteria for entry into the analysis, 24 children and adolescents with CF (S) and 14 controls (C). Sleep complaints were common in children and adolescents with CF; 43.5% reported sleep onset problem, 39.1% reported sleep maintenance problem, 30.4% were noted to snore at night, and 73.9% reported daytime sleepiness. Children and adolescents with CF had a significant decrease in sleep efficiency [SE; 75.2 +/- 2.5% (S) vs 85.6 +/- 1.7%(C); P < 0.01], prolonged rapid eye movement (REM) latency [150.5 +/- 16.6 min (S) vs 85.6 +/- 11.0 min (C); P < 0.05], and reduction in percentage of REM sleep [12.7 +/- 1.5% (S) vs 18.3 +/- 1.3% (C); P < 0.05]. The degree of sleep disruption as indicated by SE was correlated with forced expiratory volume in one second (FEV(1); r = 0.52, P < 0.05). However, there was no significant correlation between SE and minimum oxygen saturation [r = 0.30, P=not significant (NS)] or SE and maximal end-tidal pCO(2) (r = 0.11, P=NS). It is concluded that children and adolescents with CF have frequent sleep complaints and significant alteration in the sleep architecture. The magnitude of sleep disruption is associated with severity of lung disease, but is not directly correlated with the degree of nocturnal hypoxemia or hypoventilation. It is speculated that sleep disruption in children and adolescents with CF may have an impact on quality of life and clinical outcomes in this population.