Summary Despite the high sensitivity of the STOP‐Bang questionnaire [snoring, tiredness, observed apneas, high blood pressure, body mass index, age, neck size, gender] questionnaire (SBQ), which is widely used to screen individuals at high risk of obstructive sleep apnea (OSA), few studies have evaluated the discrimination related to sex in the SBQ. Therefore, our study aimed to assess whether SBQ performance is gender‐related and modified by changing body mass index (BMI) and neck circumference (NC) cut‐off values. A total of 470 patients attended the sleep centres. They were divided into moderate‐to‐severe OSA and non‐moderate‐to‐severe OSA groups based on the apnea–hypopnea index (AHI) and the results of the SBQ screening. The predictive performance of the SBQ screening instrument was evaluated by 2 × 2 contingency tables and discriminatory ability, which was estimated from the area under the curve (AUC) obtained from receiver operating characteristic curve. Our results suggest that when screening for moderate‐to‐severe OSA, the original SBQ has higher sensitivity and lower specificity for men; however, women have higher specificity and lower sensitivity. The SBQ achieved the maximum AUC of 0.783 for men and 0.634 for women when the BMI cut‐off value was established at 30 kg/m2 and the NC cut‐off value was established at 38 cm in men, and the BMI cut‐off value was established at 25 kg/m2 and the NC cut‐off value at 36 cm in women. Balancing the optimal sensitivity and specificity, the cut‐off value of the optimal modified SBQ total scores for men was determined to be ≥4 and ≥3 for women.