VDD pacing systems are an alternative to DDD pacing systems in patients with atrioven­tricular (AV) block and normal sinus node function. Our study compared atrial sensing, ventricular stimulation threshold, AV synchrony, ventricular lead impedance and quality of life in patients with VDD and DDD pacing systems. It was assumed that there are differences concerning electrostimulation and hemodynamic support between VDD and DDD pacing systems. 96 patients with implanted VDD or DDD pacing systems were enrolled prospectively into our study in 2000. The obtained data was statistically analysed using Student’s t-test for independent samples or Mann-Whitney’s t-test for two independent samples. Atrial sensing was significantly lower with the VDD system compared to the DDD system, at implan­tation and at present evaluation (p<0.001). The ventricular pacing threshold for the VDD system at implantation was significantly lower than for the DDD system (p<0.02). At the pre­sent evaluation, there was no significant difference between VDD and DDD systems (p=0.49). AV synchrony was statistically lower with VDD systems compared to DDD systems (p<0.001). The difference between the values of ventricular lead impedance at implantation and at the present evaluation was significantly lower for VDD systems compared to DDD systems (p<0.001). The quality of life did not differ significantly between VDD and DDD pacing sys­tems (p=0.96). VDD pacing systems are reliable and safe concerning electrostimulation. However, hemodynamic support is better with DDD pacing systems.