Purpose: This study was conducted to identify the factors associated with obstructive sleep apnea (OSA) risk in patients with metabolic syndrome (MS). Methods: Patients with MS between 30 and 74 years of age were recruited in an outpatient clinic of a cardiovascular center in Seoul, South Korea. MS and the risk of OSA were evaluated by Berlin questionnaire survey, the medical records of the participants were reviewed and a comprehensive lifestyle survey was performed. SPSS WIN 21.0 was used for statistical analysis. Results: BMI (OR: 1.31, CI: 1.14-1.51, p<.001) and lifestyle score (OR: 0.96, CI: 0.93-0.99, p=.028) were associated with the risk of OSA. Physical activity, weight control and diet were specifically associated with the risk of OSA after controlling for age, gender and BMI. Conclusion: This study demonstrated that lifestyle was an important factor associated with OSA risk in patients with MS.