The aim of this study was to investigate in a large population of patients with obstructive sleep apnoea and on long-term treatment with continuous positive airway pressure (CPAP) the patients' perception of symptomatic improvement, side-effects and quality of life. Questionnaires were mailed via local respiratory homecare associations to 5,339 French patients who had been treated at home for at least 6 months with CPAP machines and who continued their treatment. In total, 3,225 questionnaires were analysable. More than 80% of the responding patients reported that CPAP treatment had greatly improved their symptoms. Despite discomfort related to nasal problems and excess noise from the blower, the mean rate of use for the whole population was 6 h 36 min+/-2 h 15 min. The perceived health evaluated by the Nottingham Health Profile was good (mean score <50) for at least 75% of the patients in each dimension explored. The perceived health was significantly related to the improvement in symptoms, the overall satisfaction and the objective compliance. This retrospective study indicates that patients who continued continuous positive airway pressure treatment for more than 6 months felt a great improvement in their symptoms, were satisfied with the treatment and had a relatively good perception of their health.