Objectives: To compare right and left ventricular diastolic dysfunction in patients with chronic obstructive pulmonary disease (COPD) and bronchial asthma patients during exacerbation and in between the attacks. Patients and Methods: Group I included Thirty COPD patients(22 males and 8 females, 56 ± 10 years old).Group II included Thirty thirty asthmatic patients(20 males and 10 females, 55 ± 8 years old). Complete echo-Doppler study and spirometry were done to all patients during exacerbation and in between the attacks. Results: In group I with COPD, right ventricular wall thickness (RVWT), right ventricular end diastolic area (RVEDA) and right atrial area (RAA) were increased significantly in addition to a significant decrease in pulmonary acceleration time (ACT) and ACT/ET ratio (ET: ejection time), compared to asthmatic group II, (P