International audience Parkinson’s disease (PD) is the second most common neurodegenerative diseaseafter Alzheimer’s disease. For years, PD has been traditionally defined through motor sympto-matology, but it is now recognized that the non-motor symptoms affecting neuropsychiatric,sleep, autonomic, and sensory domains occur in up to 88% of PD patients, probably resulting ina significant source of disability. In a community-based cross-sectional study, nearly two-thirdsof patients with PD presented nighttime sleeping problems and chronic insomnia was repor-ted among one-third of patients (Gjerstad et al., 2007). This rate is three times higher thanin the general population. According to the American Academy of Sleep Medicine, cognitive-behavioral therapy for insomnia (CBT-i) is the optimal recommendation for the treatment of chronic insomnia, independent of comorbities associated or non-associated with insomnia. Infact, numerous studies have documented the efficiency of CBT-i in the treatment of chronicinsomnia comorbid with a wide spectrum of psychiatric, neurological, oncological and algologi-cal problems (Geiger-Brown et al., 2015). Furthermore, it is important to emphasize that CBTis applicable and efficient in the treatment of several problems frequently associated with PD,such as anxiety, depression and impulsive-compulsive disorders. To our knowledge, there is nospecific data relating to the use of CBT in chronic insomnia comorbid with PD. In this context,the general objective of this study was to look at the efficiency of CBT-i in the treatment ofchronic insomnia comorbid with PD, in an experimental, single-case study. This efficiency wasassessed both by short interval measures (i.e. consensus sleep diary) and by longer intervalmeasures (i.e. self-assessment questionnaires). The latter concerned complaints of insomniaas well as dysfunctional thoughts and attitudes about sleep. The patient was a 62-year-old manwho was diagnosed with PD at the age of 59. Two years after diagnosis, insomnia developed. Thepatient’s predominant daily complaint concerned dissatisfaction with both sleep quantity andquality, associated with difficulty falling sleep, and difficulty staying asleep with inability to fallback to sleep. Insomnia was associated with excessive daytime sleepiness and depressive symp-toms. CBT-i treatment was carried out over six sessions in accordance with the interventionalprotocol suggested by Morin (Morin & Espie, 2003). Psychoeducation treated sleep functioningand insomnia; sleep restriction consisted in limiting the number of hours spent in bed to thenumber of real hours of sleep; stimulus control involved instructions aimed at reinforcing theassociation between sleep and temporal and contextual indices; cognitive restructuration wascentred around dysfunctional beliefs related to sleep; education on sleep hygiene included theteaching of good sleeping habits. Finally, three post-therapeutic evaluations (at two weeks,one month and three months) were carried out by an independent assessor and included thecompletion of a sleep calendar as well as different clinical evaluation scales. The results of thevisual analysis confirmed by Wilcoxon signed-rank tests, as well as the temporal series analysis show a signification reduction in the total awakening time (−72%, Z = −3.23, P = 0.001), aswell as a significant increase in sleep efficiency (+16%, Z = −3.17, P = 0.002) between the base-line and post-therapy stage. These improvements in sleep were maintained at one and threemonth follow-ups. The average efficiency of sleep increased significantly between the base-line and one-month follow-up (+19%, Z = −3.29, P = 0.001) as well as between the baseline andthree-month follow-up (+21%, Z = −3.29, P = 0.001). At the three-month follow-up the patientno longer met the diagnostic criteria of chronic insomnia (DSM-V). Improvement in sleep wasaccompanied by improvement in mood, in daytime drowsiness, in insomnia indices such as theinsomnia severity index, in dysfunctional beliefs and attitudes about sleep and in the state ofcognitive and somatic activation prior to going to bed. This single-case study demonstrates thefeasibility and potential benefit of CBT for insomnia comorbid with PD while providing importantinformation necessary to design more definitive studies in the future.