Summary Introduction: The obstructive sleep apnea syndrome (OSAS) is a respiratory illness, characterized by recurrent episodes of apnea and hypopnea, leading to reduction or cessation of the airflow. Obesity is one of the major risk factors for the development of OSAS. To help in the diagnosis of this disease, easily applicable and low-cost questionnaries were developed, such as the Berlin Questionnaire (BQ). Objective: To evaluate the efficacy of the BQ for the screening of OSAS among candidates to bariatric surgery in a multidisciplinary preoperative program. Method: This is an observational, descriptive and cross-sectional study which evaluated obese individuals that were being prepared for bariatric surgery by means of the BQ. Results: BQ was able to detect that minimal variations in the body mass index, neck circumference and hip-to-waist ratio lead to changes in the risk to develop OSAS; the higher the values of these variables, the higher the risk for OSAS development. Conclusion: BQ was an efficient and reliable tool to demonstrate the high risk for OSAS development in individual with obesity.