Objective: To explore the demographic, anthropometric, and polysomnographic features of rapid-eye-movement (REM) related obstructive sleep apnea-hypopnea syndrome (OSAHS). Methods: This was a retrospective study of 957 patients (737 males) with either REM-related OSA (REM-OSAHS group) (n=157) or non-rapid-eye-movement (NREM) related OSA (NREM-OSAHS group) (n=800). The patients diagnosed with REM-OSAHS were classified as the wide definition (REM1 group), the traditional definition (REM2 group) and the strict definition (REM3 group). The differences in demographic and polysomnographic characteristics were compared in three groups. Results: The REM-OSAHS group was lower than the NREM-OSAHS group in terms of the Body Mass Index (BMI), the neck circumference, and The Epworth Sleeping Scale (ESS). The NREM-OSAHS group was significantly higher than of the REM-OSAHS group in terms of the overall mean AHI (combined in all sleep stages), the oxygen desaturation index (ODI) and the mean AHI in the supine position (s-AHI). The SpO2 Conclusions: These data suggest that frequency and severity of sleep apnea is lower in REM related OSAHS patients, and they are presenting with specific characteristics in demography, anthropometry. Furthermore, the more apnea hypopnea events associated with REM sleep, the less severe the condition. Keywords: Sleep apnea,obstructive;Apnea; Rapid eye movement sleep; Anthropometry;polysomnography