Background Differentiation between ischemic (ICM) and dilated cardiomyopathy (DCM) has important therapeutic implications because the former may benefit from coronary revascularization. The aim of this study was to investigate right ventricular (RV) function using tissue Doppler echocardiography (TDE) and compare the TDE parameters of the RV among patients with ICM and DCM. Methods and Results Forty-two patients with ICM and 40 patients with DCM were studied with conventional echocardiography and TDE. The 2 groups did not differ in terms of New York Heart Association class, left ventricular ejection fraction and pharmacological treatment. Patients with ICM had higher pulmonary artery systolic pressure (44.4 mmHg vs 34.7 mmHg, p=0.006) and lower tricuspid annular motion systolic (RV Sa 0.06 m/s vs 0.09 m/s, p<0.0001), and diastolic velocities (RV Ea 0.05 m/s vs 0.07 m/s, p=0.0003, RV Aa 0.075 m/s vs 0.11 m/s, p=0.0016). They also exhibited a higher ratio of early transtricuspid filling velocity to early diastolic velocity of the tricuspid annulus (RV E/Ea 8.2 vs 5.7, p=0.0008). Age, pulmonary artery systolic pressure and tricuspid Sa were significant independent predictors of the diagnosis of ICM. Conclusions RV dysfunction is more pronounced in patients with ICM than in patients with DCM. The RV TDE parameters can be used to complement clinical and conventional echocardiographic findings in the assessment of patients with ICM and DCM. (Circ J 2008; 72: 238 - 244)