Background: Undiagnosed obstructive sleep apnoea (OSA) is a risk factor for postoperative atrial fibrillation (POAF) as well as for heart disease in general. This necessitates screening during preoperative assessment to facilitate the implementation of strategies to minimise the postoperative risk. Overnight polysomnography is the " gold standard" for the diagnosis of OSA but may be impractical during preoperative assessment, and so questionnaires may be useful for screening OSA. The Berlin Questionnaire (BQ) and Epworth Sleepiness Scale (ESS) are two of the widely prescreening tools for persons who may suffer from sleep disorders. Thus, screening for and treating OSA as part of the routine preoperative evaluation of cardiac surgical patients may be a useful strategy for preventing POAF. Objective: We investigated whether there is an association between POAF and sleep disorders evaluated by the BQ and ESS in this settings. Methods: In 73 consecutive patients undergoing CABG with cardiopulmonary bypass, preoperative clinical characteristics and operational data were examined. During the clinical evaluation, all patients answered the ESS and BQ voluntarily upon admission. Patients were continuously monitored for the occurrence of sustained postoperative AF while hospitalised. Results: There were 33 patients with POAF and 40 patients without POAF as age- and gender-matched controls. The prevalence of high score in ESS was higher in POAF group compared to control group (52% vs 27%; p: 0.030). There was a higher prevalence of high risk for OSA in BQ in the POAF group (58% vs 34%; p: 0.044). Conclusion: Preoperative questionnaire-based diagnosis of OSA by the simple BQ and ESS may be useful in predicting POAF, and can be easily incorporated into routine screening of surgical patients undergoing CABG operation. © 2012 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ).