Objective: To evaluate the effectiveness of the Berlin and STOP-BANG questionnaires in screening patients at high risk for obstructive sleep apnea. Subjects and methods: A cross-sectional study of 107 patients suspected of having obstructive sleep apnea at the National Lung Hospital. Results: 34.6% of patients participating in the study had a Berlin score predicting a high risk, 56.1% of patients participating in the study had a STOP-BANG score predicting a high risk of obstructive sleep apnea. The number of patients with sleep apnea at different levels when recording respiratory polygraphy accounted for 91.6% of patients participating in the study. Patients with a high-risk STOP-BANG score were 2.45 times more likely to have moderate-severe OSA than patients with a low-risk STOP-BANG score. The positive diagnostic value of both questionnaires is above 90%. Conclusion: The Berlin questionnaire has higher specificity, which helps to better orient the diagnosis. Meanwhile, the STOP-BANG questionnaire has higher sensitivity, which helps to better screen.