Cardiac resynchronization therapy has been an effective option in patients with advanced heart failure. However, 20 to 30% of the patients do not benefit from this therapy. Clinical, electrocardiographic and echocardiographic criteria have been studied in an attempt to select patients who will benefit from a cardiac resynchronization therapy, and the echocardiogram is important both in the selection and in the evaluation and optimization of the therapy. The objective of this review is to describe the main echocardiographic parameters used in the evaluation of the cardiac resynchronization therapy.