Background: While sleep disruption is a common complaint among children with cystic fibrosis (CF), only a few studies have investigated insomnia in adults. The aim of this study was to identify factors associated with insomnia in clinically stable adult CF patients.Methods: Twenty-eight CF patients (18M/10F), with a mean age of 28.2 ± 8.5 (mean ± standard deviation) years and a mean forced expiratory volume in one second of 69 ± 31% predicted completed questionnaires on insomnia (Insomnia Severity Index, ISI), sleep quality (PSQI), daytime sleepiness (Epworth), restless legs syndrome (IRLS), pain (NRS), anxiety/depression (HAD) and quality of life (CFQ-R 14+). Respiratory assessment data, including symptoms, sputum analysis, arterial blood gases, 6-minute walking test, pulmonary function tests and polysomnographic variables, were also analyzed. Results: Forty-three percent of patients were insomniac (ISI > 7). Compared with non-insomniac patients (ISI ≤ 7), insomniac patients had more severely impaired quality of life and a higher HAD score: mean anxiety score of 8.9 ± 2.4 vs 4.0 ± 2.4 (p <0.001), mean depression score of 7.3 ± 3.4 vs 2.1 ± 2.2 (p <0.01), with a positive correlation between ISI and HAD anxiety/depression scores (r=0.674/r=0.724, respectively, p <0.001). Insomnia was also associated with restless legs syndrome, pain and lower SpO2 during sleep. Conclusions: The strong association between insomnia, impaired quality of life and increased HAD score should prompt physicians to be particularly attentive to the management of anxiety and depression in adult CF patients with insomnia.Trial registration: on clinicaltrials.gov (NCT02924818)