Cystic fibrosis is a chronic, life-shortening illness that affects multiple systems and results in frequent respiratory infections, chronic cough, fat malabsorption and malnutrition. Poor sleep is often reported by patients with cystic fibrosis. Although objective data to explain these complaints have been limited, they do show poor sleep efficiency and frequent arousals. Abnormalities in gas exchange are also observed during sleep in patients with cystic fibrosis. The potential impact of these abnormalities in sleep on health and quality of life remains largely unstudied. This review summarizes what is known about sleep in children with cystic fibrosis, and implications for clinical practice. This report also highlights new evidence on the impact of sleep problems on disease-specific outcomes such as lung function, and identifies areas that need further exploration.