Backround: The aim of the present observational study is to search the incidence of postoperative atrial fibrillation (AF) in patients with or without preoperative statin treatment. Methods and Results: The population consisted of 362 consecutive patients (267 on and 95 not on statin). Diabetes mellitus was more frequent in statin group (p = 0.03). Other demographic and procedural variables were similar in the both groups (All p > 0.05). Postoperative AF was less frequent and its duration was shorter in statin group compared to non-statin group (p = 0.03 and 0.0001, respectively). The Kaplan-Meier analysis showed the protective effect of statins against the risk of developing AF (p = 0.01). Conclusion: Statin treatment before the by-pass surgery decreases the incidence and shortens the duration of postoperative AF.