Objectives: Carvedilol and bisoprolol reduce QT dispersion (QTD) in chronic heart failure (CHF). However, it is unclear whether there is a difference between the effects of the two drugs. The aim of the present study was to compare the long-term effects of carvedilol and bisoprolol on QTD in patients with CHF. Methods: Eighty-one patients with CHF with no previous β-blocker therapy were included in this prospective study. The patients were randomly allocated to carvedilol or bisoprolol therapy. Left ventricular ejection fraction (LVEF), heart rate (HR), QTD, and corrected QTD (QTcD) were calculated at baseline and at the 6th month of therapy. Results: In comparison to baseline values in both therapy groups, LVEF was significantly improved, and a statistically significant decrease was found in HR (carvedilol from 76 ± 12 to 65 ± 10 beats/min, p < 0.001; bisoprolol from 78 ± 13 to 65 ± 8 beats/min, p < 0.001) and QTcD (carvedilol from 85 ± 28 to 65 ± 22 ms, p < 0.001; bisoprolol from 83 ± 22 to 61 ± 20 ms, p < 0.001). In our study, carvedilol and bisoprolol were found to have similar effects on LVEF, HR, and QTcD. Conclusions: Carvedilol and bisoprolol decrease HR and QTcD in patients with CHF, and there is no meaningful difference between the two β-blockers as regards their effects on these parameters. Copyright © 2008 S. Karger AG.