Background: Dysfunction of sinoatrial node is a set of abnormal rhythms which are resulted from the sinoatrial node malfunction of the sinus node, the chief natural cardiac pacemaker. The common, and occasionally, the single method for treatment of heart arrhythmias was implantation of pacemaker, which reduce symptoms exactly occurs after implantation. Aim: To detect the role of smoking on cardiac electrophysiology parameters in sinus node dysfunction in Iraqi patients such as SNRT and AH. Methods: A cross sectional study, was conducted on 59 patient ranging between 20-50 years old and involving 35 female and 24 male patients, suffering from an unexplained symptoms of sinoatrial node dysfunction (SND). The enrolled participants were gathered from patients who visited the arrhythmia consultant clinic in the Najaf center for cardiac surgery and interventional catheterization at Al-Sadr Medical City in Najaf from all parts of Iraq. The duration of study extended from the beginning of July 2018 till the ending of July 2019. The patients were selected and investigated according to inclusion criteria and either referred to electrophysiological study, pacemaker implantation and/or implantable loop recorder accordingly. Results: The basic procedure of the study was measurement of cardiac electrophysiological parameters such as SNRT and AH as well as other noninvasive investigations such as PR. Depending on sinus node recovery time (SNRT) measurement for all patients, new cutoff point (1150 milliseconds) for pacemaker implantation was detected. Statistically significant correlations were found between new SNRT cutoff of study and most of electrophysiological, anthropometric, demographic that achieved in current study (P-value 0.05). Conclusion: The principal conclusion of this study was that smoking has a significant effect on PR, SNRT, and AH parameters of patients with unexplained symptomatic SND in Iraq. © 2020 Lahore Medical And Dental College. All rights reserved.