Background:Cardiac resynchronization therapy (CRT) is now an established effective treatment for patients with advanced heart failure. One approach to improve CRT outcome may be determination of the degree of dsynchrony before CRT as a predictor for CRT response. Conversely, the focus may be on an improved positioning of CRT left ventricular (LV) lead. AIM of the study: We aimed at our study to define the rule of three-dimensional echocardiography in determining the optimal site of LV pacing lead. Patients and Methods: The current study was conducted on 30 patients with heart failure who had received CRT in Ain Shams University Hospitals in the period from 2012 to 2014. All patients were subjected to thorough history taking, complete general and local examination, conventional 2D echo and 3D echo analysis. The latest wall to reach the minimal volume was determined. The patients were classified after CRT insertion into group A with concordance between the delayed LV area and LV lead position and group B with discordance between them. Our patients were followed up for 6 months duration. Results: Our findings demonstrated that the response to CRT resulted in improvement of NYHA class (p-value 0.04), LV EF by 2D and 3D echocardiography (P value <0.001 for both) with significant increase in LV 3D SV (p value 0.001), and significant reduction of LA diameter (p-value 0.03), LVESD diameter, 2D and 2D LVESV (P value 0.026, 0.026  respectively), however there was no any statistically significant difference between both groups. Conclusions: No additional benefit of selecting LV lead position pre CRT insertion to be concordant with the latest myocardial segment in reaching the minimal systolic volume assessed by 3D echocardiography