Background: Coronary Artery Disease (CAD) is generally characterized by episodes of reversible myocardial demand/supply mismatch, related to ischemia or hypoxia. P wave peak time (PWPT) is a newly introduced electrocardiographic parameter that has been shown to be associated with noreflow in patients with acute coronary syndrome (ACS). This study aimed to evaluate whether there is any association between prolonged PWPT in ECG and the severity of CAD in diabetic patients. Patients and methods: This study included 134 diabetic patients with history of coronary artery disease and were admitted to cardiology department Zagazig University. Patients were divided into group (I) of 40 patients with no evidence of obstructive CADs and group (II) of 94 patients with evidence of obstructive CADs. Results: The difference between both groups was statistically significant regarding the PWPT in lead II and V1. There was a significant difference between both groups concerning the R-wave peak time as the mean value in group I was 21.4 ± 3.7 while in group II was 29.2 ± 7.1. Regarding QRS duration, there was statistically significant increase in group II than in group I. Group II had statistically significant increase in PWD max, PW dispersion and PWTF in the lead V1 than group I. Regarding PWD min, there was no statistically significant difference between the two groups. The cut off value of PWPT in the lead II was 56.5msec with sensitivity (62.8 %) specificity was (80.0 %) and accuracy was 68.6 % .The PWPT in the lead V1, had a cut off value 54.5msec with sensitivity, specificity and accuracy were (66.0 %, 75.0 % and 67.9 %) respectively. the mean value of left ventricular ejection fraction in group I was 63.1 ± 8.3 while it was 53.5 ± 11.6 in group II. There was statistically significant increase in LVEF % among group I than group II. Group II had statistically significant increase in left atrial diameter than in group I (33.4 ± 4.1mm in group I vs 38.2 ± 11.6mm in group II). Conclusion: Prolonged P-wave peak time (PWPT) is a beneficial parameter for detecting high-risk patients with stable coronary artery disease. There was statistically significant older age among patients with obstructive coronary artery disease than those with non-obstructive coronary artery disease. Obstructive CAD group had statistically significant increase in left atrial diameter, left ventricular dilatation. Also, there was statistically significant increase in LVEF % among non-obstructive coronary artery than obstructive coronary artery disease one.