OBJECTIVE This study aimed at comparing the development of tricuspid and mitral regurgitation between the right ventricular outflow tract (RVOT) and right ventricular apex (RVA) pacing. METHODS We prospectively enrolled 164 patients for permanent pacemaker implantation due to sick sinus syndrome or atrioventricular block and randomly divided them into two equal groups to receive either RVOT or RVA pacing. Patients with heart failure or valvular disease were excluded. The post-procedural echocardiographic evaluations were performed 1 year after the pre-procedural echocardiography, and the results were compared with respect to the development of mitral and tricuspid regurgitation and probable changes in the ejection fraction (EF). RESULTS Age, gender, pacing mode, and baseline cardiac rhythm did not significantly differ between the RVOT and RVA pacing groups. The incidence of mitral regurgitation was significantly higher in the RVA group (p = 0.03), but the incidence of tricuspid regurgitation was similar in both groups. There was a trend toward less tricuspid regurgitation in the RVOT group; however, it was not statistically significant. The mean EF was not significantly different between the study groups. CONCLUSIONS It seems that the incidence of mitral regurgitation in RVA pacing is significantly higher than that in RVOT pacing. The formation of tricuspid regurgitation needs to be discussed in the future. BACKGROUND IRCT201103146061N1.