Background: Conventional risk factors for the development of CAD (Coronary Artery Disease) have an adverse influence on prognosis in those with established disease. P wave peak time (PWPT) as Electrocardiography (ECG) parameter, has been shown to be associated with imperfect reperfusion in patients with acute coronary syndrome (ACS).The aim of the present study was to investigate whether there is any association between prolonged PWPT in ECG and the severity of CAD detected by SYNTAX score in diabetic patients. Patients and methods: A cross sectional single center study was conducted on a total of 134 consecutive diabetic patients with history of stable coronary artery disease, in which coronary angiography was indicated, and were admitted to cardiology department Zagazig University. Patients were divided into group (I) included 40 patients with no evidence of obstructive CADs and group (II) included 94 patients with evidence of obstructive CADs. Invasive coronary angiography was performed via radial and femoral approaches according to Judkins technique. We select calculation of SYNTAX scores. Results: The mean SYNTAX Score among the obstructive coronary artery disease group was (20.97 ± 13.8) where about half of the group (55.3%) had low SYNTAX Score, (24.5%) had intermediate and (20.0%) had high SYNTAX Score. Left atrial diameter had statistically significant increase in high than intermediate than low syntax score groups (44.2 ± 4.4mm vs 37.9 ± 52mm vs 36.1 ± 4.7mm) respectively. Hypertension and dyslipidemia found to be statistically related to the severity of CAD (P= 0.01*, 0.002* respectively). There was significant statistical relation between QRS duration and the coronary artery disease severity (P=0.02*). Conclusion: Prolonged P-wave peak time (PWPT) which is a parameter easily obtainable from the ECG, is associated with the severity and complexity of coronary artery disease (CAD) detected by syntax score in diabetic patients with stable coronary artery disease. It might be useful for identifying high-risk patients with stable coronary artery disease. Therefore, it could be beneficial in risk stratification of patients with CAD.