An apparatus comprises a cardiac signal sensing circuit, a stimulus circuit, and a control circuit. The control circuit includes a pacing site locating circuit that initiates a first electrical stimulus from a first electrode positioned in or near a first ventricle of a heart, determines a first time interval between delivery of the first electrical stimulus and a subsequent cardiac event sensed at a selectable electrode location in or near a second ventricle of the heart, initiates a second electrical stimulus at the selectable electrode location in or near the second ventricle, determines a second time interval between delivery of the second electrical stimulus and a subsequent cardiac event sensed at the first ventricle, calculates a difference between the first and second time intervals, and generates an indication of a preferred pacing site in the second ventricle according to the calculated differences between the first and second time intervals.
