Background: Ischemic heart disease is a major cause of heart failure and has a poor prognosis. Addressing behavioral risk factors like obesity and overweight helps avoid most cardiovascular illnesses. The satiety hormone leptin reduces appetite and regulates energy. Aim of the study: Leptin levels in lean and obese patients with ischemic heart disease, with or without diastolic dysfunction, were compared. Methods and Patients: Between June 2019 and November 2020, 140 ischemic patients from Ain Shams University hospitals were included. History, examination, Duke Coronary Artery Disease score, Body Mass Index, serum leptin, and echocardiography were recorded. Patients were placed into four BMI and diastolic function groups plus the control group. A: lean ischemic patients without significant diastolic dysfunction, B: lean ischemic patients with diastolic dysfunction (II-IV), C: obese ischemic patients without significant diastolic dysfunction, Group D: obese ischemic patients with diastolic dysfunction, and E was a control group. Results: A positive correlation was seen between serum leptin and Duke score in all ischemia groups (n=140) (p < 0.001). Serum leptin was higher in diastolic dysfunction groups (n=70) than in non-dysfunction groups (N=70) (Group B 25.7%, Group D 28.6% vs Group A 5.7%, Group C 8.6%, and Control Group (n=35) 0.0%). Conclusion: Leptin independently increases CAD risk. In CAD patients, elevated leptin was related to diastolic dysfunction.