BACKGROUND The present study aimed to investigate the risk factors associated with demographical, clinical and polysomnographic features of positional sleep apnea through different criterion of positional sleep apnea (POSA vs e-POSA) in a large patient cohort from a tertiary referral center MATERIAL AND METHODS A total of 782 OSA patients who were further diagnosed with POSA (total: n=470, e-POSA: n=204) or non-POSA (n=312) based on apnea-hypopnea index (AHI) events by overnight polysomnography were included. Demographical, clinical, and polysomnographic characteristics were recorded, while independent predictors of POSA and e-POSA were determined via linear regression analysis. RESULTS Severe OSA (AHI ≥30/h) was less common in the POSA (33.4% vs 71.5%, P<0.001) and e-POSA (9.8% vs 62.3%, P<0.001) groups than in the non-POSA and non-e-POSA groups, respectively. For POSA and e-POSA, male sex (OR 2.195, P<0.001 and OR 2.021, P=0.004, respectively), low body mass index (BMI; OR 0.932, P<0.001 and OR 0.948, P=0.006), low AHI (OR 0.954 and OR 0.902, P<0.001 for each), and less desaturation (T90%, OR 0.972 and OR 0.968, P<0.001 for each) were the common statistically significant predictors. Younger age was an independent predictor of POSA (OR 0.97, P=0.003). POSA (median 20.4 s) and e-POSA (20.5 s) groups demonstrated similar apnea-hypopnea durations (min) as the non-POSA (median 21.1 s) group. CONCLUSIONS Our findings revealed that male sex and lower values of BMI, AHI, and desaturation were common determinants of POSA and e-POSA, while younger age independently predicted POSA. POSA and e-POSA had similar clinical and polysomnographic characteristics and shared the unvaried hypoxic burden.