In our study, we assessed sexual function in patients with obstructive sleep apnea syndrome (OSA). Our study was cross-sectional, descriptive and case-control analytic, involving OSA patients recruited from a sleep unit. We used the Epworth Sleepiness Scale, the International Index of Erectile Function Scale, the Female Sexual Function Index Scale, the Hospital Anxiety and Depression Scale and the Sexual Satisfaction Index to assess daytime sleepiness, sexual function, anxiety and depressive symptoms and sexual satisfaction respectively. The prevalence of sexual dysfunction (SD) was 56.5% in men and 71.4% in women. Patients presented anxious symptomatology in 36.4% and depressive symptomatology in 29.5%. Compared with controls, SD was more frequent, and the mean marital sexual dissatisfaction score was significantly higher in patients. Hence the importance of assessing sexual function in these patients in order to improve their quality of life.