Cardiac resynchronization therapy is an established approach for the treatment of patients with heart failure and left ventricular systolic dysfunction. In most centers, these patients are usually evaluated by echocardiography, which allows collecting a number of cardiac anatomical and functional parameters in a non-invasive, repeatable way and without exposure to ionizing radiation. However, over the years, clinical studies have sometimes emphasized and sometimes reduced the role of this method in the setting of cardiac resynchronization therapy for cardiac dyssynchrony evaluation, prognostic stratification of patients, optimization of pacing, and follow-up. The purpose of this paper, therefore, is to review the current role of echocardiography before, during and after the implantation of a cardiac resynchronization therapy device.