The aim of this study was to determine which of the clinical parameters are the most valuable in predicting postoperative atrial fibrillation after lung surgery. Retrospective analysis was carried out on 298 patients after pulmonary resection necessitated mainly by lung cancer. The following parameters were investigated: age and sex, disturbances of cardiac rhythm, history of ischemic heart disease, diabetes and atherosclerosis, NYHA classification and type of surgical procedure. In addition, the duration of surgery, variations in oxygen saturation, changes in systemic blood pressure and heart-rate were noted intraoperatively. Statistical analysis was performed using Fisher's exact test. Atrial fibrillation occurred in 25 cases (8.4%) and more frequently after pneumonectomy (24%). Other factors contributing to atrial fibrillation after lung surgery were: history of ischemic heart disease, congestive heart failure, intraoperative cardiac arrest and the need for rethoracotomy.