Response to cardiac resynchronization therapy is predicted for a given stimulation site so that an atrioventricular delay of an implantable device administering cardiac resynchronization therapy may be set to a proper amount. The first deflection of ventricular depolarization is measured, such as through a surface electrocardiogram or through an intracardiac electrogram measured by a lead positioned in the heart at the stimulation site. The maximum deflection of the ventricular depolarization is then measured by the lead positioned at the stimulation site. The interval of time between the first deflection and the maximum deflection of the ventricular depolarization is compared to a threshold to determine whether the stimulation site is a responder site. If the interval is larger than the threshold, then the site is a responder and the atrioventricular delay of the implantable device may be set to less than the intrinsic atrioventricular delay of the patient. Otherwise, the atrioventricular may be set to approximately equal the intrinsic atrioventricular delay.