Background: Cardiac resynchronization therapy (CRT) is an effective treatment in patients with heart failure (HF), low left ventricular ejection fraction (LVEF) and wide QRS. However, there are a percentage of these patients who are non-responders, implying worse clinical outcomes.Objectives: The aim of this study was to assess the differences in echocardiographic parameters of reverse remodeling and event rates [hospitalization for heart failure (HHF), all-cause mortality (ACM), heart transplantation (HTX) and appropriatetherapies (AT)] between responder vs. non-responder patients to CRT.Methods: A total of 343 patients with CRT, classified into responders and non-responders according to clinical and echocardiographic parameters, were included in the study. A 2-year follow-up was performed, in which reverse remodeling and the incidence of HHF, ACM, HTX and AT were evaluated.Results: Among the 343 patients, 17% were non-responders and 83% responders. At 6 and 12 months there were no significant differences in ventricular diameters, but significant differences in LVEF (p<0.001), with greater increase in responders.At 24 months, responders had smaller diastolic diameter (p=0.004), smaller systolic diameter (p=0.003) and higher LVEF (p<0.001). Non-responders had significantly higher incidence of HHF (p<0.001), HTX (p=0.001) and AT (p=0.002), and an excess of ACM at the limit of statistical significance (p= 0.056).Conclusions: Patients responding to CRT presented greater reverse remodeling and better clinical evolution, in accordance with the results of international observational studies. How to cite this article: Santillán ME, Galizio NO, Amrein ME, Favaloro LE, RENEDO MF, CARNERO GA, Mysuta M, González JL. Cardiac Resynchronization Therapy. Long-Term Evolution of Responder and Non-Responder Patients. Rev Argent Cardiol 2024;92:211-6. http://dx.doi.org/10.7775/rac.v92.i3.20771