Cardiac resynchronization therapy (CRT) is an effective treatment of heart failure in selected patients. However, with conventional CRT, notable left ventricular (LV) reverse remodelling is achieved in only 60-70% of patients. This lack of effect of CRT might be due to incomplete resynchronization. In some patients, the paced activation front arising from a single LV electrode is unfavourable, possibly resulting in suboptimal resynchronization. Dual-site LV CRT has theoretical advantages in faster and more physiological LV activation. Some clinical evidence supports dual LV pacing. Nevertheless, a clear benefit of this pacing modality in patients chronically implanted is still unproved. A randomized study comparing single- and dual-site LV pacing, the Triple-Site Cardiac Resynchronization study of Patients with Heart Failure (TRUST CRT) is still ongoing.