Introduction: The aim of our study was to analyze the effects (clinical, electrical as well as echocardiographic) of cardiac resynchronization therapy devices with or without an implantable defibrillator (CRT-P and CRTD devices, respectively) on heart failure patients. Methods: We retrospectively analyzed 131 patients implanted with a cardiac resynchronization device (CRTP and CRT-D) at Timișoara Institute of Cardiovascular Diseases between 1st of January 2003 and 1st of June 2014. Patients were between 26 and 86 years of age, with an average of 61 years. In evaluating the effects of the cardiac resynchronization therapy we focused on New York Heart Association Functional Class (NYHA Class), on changes in QRS duration on the surface ECG and on the left ventricular ejection fraction as measured by echocardiography. The parameters were measured several days before the implantation and again after at least 1 month. Results: Mean QRS duration shortened from an average duration of 155 ms to 129 ms, a statistically significant shortening of 26.5 ms (95% CI, 19 ms – 33 ms), p < 0.0001. The left ventricular ejection fraction increased from an average of 30% to an average value of 35% (p = 0.0011). NYHA Functional Class improved significantly (p < 0.0001). Conclusions: Implantation of a Cardiac Resynchronization Device provides benefits for heart failure patients. In our retrospective cohort experience, we found a strong correlation between electrical changes, echocardiographic improvement and clinical function improvements.