RATIONALE: Obstructive sleep apnea is highly prevalent in children with asthma, particularly in obese children. The sleep related breathing disorder screening questionnaire has low screening accuracy for obstructive sleep apnea in children with asthma. Our goal was to identify the questions on the sleep related breathing disorder survey associated with obstructive sleep apnea in children with asthma. METHODS: Participants completed the survey, underwent polysomnography and their body mass index z-score was measured. Participants with survey scores above 0.33 were considered high risk for obstructive sleep apnea and those with an apnea hypopnea index ≥ 2 events/hour classified as having obstructive sleep apnea. Logistic regression was used to examine the association of each survey question and obstructive sleep apnea. Positive and negative predictive values were calculated to estimate screening accuracy. RESULTS: The prevalence of obstructive sleep apnea was 40% in our sample (n=136). Loud snoring, morning dry mouth and being overweight were the questions associated with obstructive sleep apnea. A combined model of loud snoring, morning dry mouth and being overweight had positive and negative predictive values of 57.4% and 81.0% respectively, while the composite survey score had positive and negative predictive values of 51.0% and 65.5%. Body mass index z-score had positive and negative predictive values of 76.3% and 72.2%. CONCLUSIONS: The body mass index z-score is useful for obstructive sleep apnea screening in children with asthma and should be applied routinely given its simplicity and concerns that obstructive sleep apnea may contribute to asthma morbidity.