Heart failure frequently occurs in patients with preserved or minimally impaired systolic function. Diastolic dysfunction plays a crucial role in this type of heart failure, which is called “diastolic heart failure” or “heart failure with preserved ejection fraction.” The clinical burden of this type of heart failure is now widely recognized. We discuss the importance of assessing diastolic function. However, most of the parameters available today are indices for left ventricular (LV) filling pressures, which change secondary to LV diastolic dysfunction and cannot directly assess diastolic function. LV diastolic function comprises LV relaxation and LV stiffness, and LV stiffening follows LV relaxation and induces the transition from asymptomatic to symptomatic diastolic dysfunction. Recently, the usefulness of color kinesis and speckle tracking echocardiography in assessing LV relaxation has been reported. We propose assessing LV stiffening (distensibility), an index derived from the movement of the epicardial site of the LV wall and overlooked in routine echocardiography. Future studies should clarify the clinical significance of these new parameters and lead to new methods.