Aim. To compare patients with bradyarrhythmias and obstructive sleep apnea (OSA) and patients without OSA; to study the predictive capabilities of questionnaires in OSA screening.Material and methods. The study included 134 patients with bradyarrhythmias hospitalized for pacemaker implantation or pacemaker replacement. The median age was 67.5 years (interquartile range 59 to 72 years). Sleep apnea screening was performed using the Berlin questionnaire, the STOP-BANG sleep apnea risk scale, and the Epworth sleepiness scale. All patients underwent blood tests and instrumental examinations (respiratory monitoring and echocardiography).Results. Patients with OSA were older (68 years versus 64 years; p = 0.032), had a larger waist circumference (116 cm versus 108 cm; p = 0.044), and body mass index (33.7 kg/m2 versus 31.03 kg/m2; p = 0.016) compared to patients without OSA. The Berlin questionnaire (area under the curve (AUC) 0.79; sensitivity 92 %, specificity 38 %; p <0.0001) and the STOP-BANG risk scale (AUC 0.75; sensitivity 82 %, specificity 23 %; p <0.0001) had a high predictive power to identify sleep apnea while the Epworth sleepiness scale had a low predictive power (AUC 0.463; sensitivity 12 %, specificity 85 %). According to laboratory and instrumental data, patients with sleep apnea had significantly higher C-reactive protein levels (7.17 mg/L versus 1.73 mg/L; p = 0.012) and more frequently had interventricular septal hypertrophy (12 mm versus 10 mm; p = 0.02). Third-degree atrioventricular block was significantly more common in patients with sleep apnea (17.91 % versus 5.97 %; odds ratio 0.363; 95 % confidence interval 0.131–1.001; p = 0.045). In patients with sleep apnea, cardiac pacing for more than 5 years was more common (11.94 % versus 4.48 %; odds ratio 0.35; 95 % confidence interval 0.116–1.054; p = 0.049).Conclusion. High frequency of OSA was observed in patients with bradysystolic heart rate. The Berlin questionnaire and the STOP-BANG sleep apnea risk scale can be used to screen for OSA in patients with bradyarrhythmias. Elevated C-reactive protein levels and interventricular septal hypertrophy accentuate the importance of early diagnosis and treatment of OSA for improved prognosis.