Cardiac resynchronization therapy can treat chronic heart failure through either biventricular pacing (BVP) or isolated left ventricular pacing (LVP), and the efficacy is depended on QRS duration. However, the optimal therapeutic choice of pacing or how the QRS influences the efficacy remains uncertain. To investigate this uncertainty, we searched available publications in PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials databases regarding differentials in efficacy parameters between BVP and LVP. A meta-analysis of eight randomized controlled trials found that BVP and LVP were comparable with regard to quality-of-life scores, left ventricular ejection fraction, left ventricular end-systolic volume, and mortality or heart transplant rates. However, there was a significant heterogeneity among the trials in 6-min walking distances. Subsequent meta-regression indicated that the baseline QRS duration significantly correlated with the standard mean difference between BVP and LVP. As QRS duration increased, the gain in 6-min walking distance with BVP became significantly greater than that of LVP. This suggests that it is necessary to consider the QRS duration when comparing the clinical effects of BVP and LVP.