Background/aim: The aim of this study was to investigate alterations in voice parameters among patients using continuous positive airway pressure (CPAP) for the treatment of obstructive sleep apnea syndrome. Materials and methods: Patients with an indication for CPAP treatment without any voice problems and with normal laryngeal findings were included and voice parameters were evaluated before and 1 and 6 months after CPAP. Videolaryngostroboscopic findings, a self-rated scale (Voice Handicap Index-10, VHI-10), perceptual voice quality assessment (GRBAS: grade, roughness, breathiness, asthenia, strain), and acoustic parameters were compared. Results: Data from 70 subjects (48 men and 22 women) with a mean age of 44.2 ± 6.0 years were evaluated. When compared with the pre-CPAP treatment period, there was a significant increase in the VHI-10 score after 1 month of treatment and in VHI- 10 and total GRBAS scores, jitter percent (P = 0.01), shimmer percent, noise-to-harmonic ratio, and voice turbulence index after 6 months of treatment. Vague negative effects on voice parameters after the first month of CPAP treatment became more evident after 6 months. Conclusion: We demonstrated nonsevere alterations in the voice quality of patients under CPAP treatment. Given that CPAP is a long-term treatment it is important to keep these alterations in mind.