Cardiac resynchronization therapy (CRT) improves measures of systolic function and clinical status. However, its effect on diastolic function is not well established. Commonly used parameters of diastolic function are measured from echocardiography, using pulse wave and tissue Doppler technologies, as well as timing and deformation data. Review of the existing studies that address the relationship between diastolic function and CRT shows conflicting data, but general trends can be deduced. Baseline elevated filling pressure appears to identify patients most likely to derive improvement in that particular parameter. Intrinsic relaxation does not appear to be significantly impacted by CRT. Generally, changes in diastolic properties after CRT appear to be linked to changes in systolic function. Specific therapy aimed at diastolic asynchrony is lacking, partly due to an unclear relationship between diastolic asynchrony and diastolic dysfunction, and the inability to specifically impact diastolic timing with a systolic intervention such as CRT.