Objective: To compare patients who underwent the Bidirectional Glenn Operation with and without cardiopulmonary bypass (CPB), analyzing the characteristics and confirming if there is superiority of either of the employed techniques. patients with complex heart defects were submitted to this operative technique. The mean age of the patients was 19 months and 14 were female. The patients were divided into two groups: Group A with 7 patients (using CPB) and group B with 9 patients (without the use of CPB). Gender, age, mean pulmonary artery pressure (MPAP), CPB time, aortic clamping time, venoatrial shunt, previous operations, time in intensive care unit (ICU), total hospitalization time and immediate complications were all compared between the two groups.Results: The median MPAP was 13 mmHg. In group A the CPB time was 91 ± 47 minutes (57-195 minutes), myocardial ischemia was 25 ± 33 minutes (0-80 minutes). Of these, four patients required intracardiac procedures or enlargement of the pulmonary branches and in three, CPB assistance as ventilatory support was needed. In group B the venoatrial shunt was 21 ± 10 minutes (0-39 minutes). The time to extubation was 9 ± 13 hours with a median of 3 hours (1-43 hours). The ICU stay was 8 ± 12 days with a median of 5 days (1-50 days). Hospitalization was 12 ± 12 days with a median of 7 days (0-50 days). Five patients had been submitted to surgeries previously. Two, one patient from each group, died (12.5%). No neurological complications, pleural or pericardial effusions were observed. No significant differences were evidenced between the two groups in respect to all the variables studied.Conclusion: In spite of the relatively small cohort, this study suggests that the bidirectional Glenn operation can be performed with or without CPB giving similar results in respect to morbidity and mortality. Thus, the operation without CPB can be safely employed when the anatomic findings are appropriate and there is no severe hypoxia.