Background. P-wave dispersion has been shown to be a noninvasive electrocardiographic predictor for development of atrial fibrillation. Thus it may be possible to attenuate atrial fibrillation risk through normalization of P-wave variables and improvement in P-wave dispersion may be an important goal in treatment of hypertension. Objective. To compare the effects of nebivolol, a new P-blocker that have additional vasodilating activity via acting on endothelium and nitric oxide release, and atenolol on P-wave duration and dispersion in patients with mild-to-moderate hypertension. Methods. A total of 34 newly-diagnosed hypertensive patients were enrolled in the study. The patients were randomly assigned to receive treatment with either nebivolol (5 mg) or atenolol (50 mg). P-wave durations (Pmin and Pmax) and P-wave dispersion were measured before and one month after treatment. Results. While Pmin increased (50,6 +/- 11,2 ms to 54,7 +/- 9,1 ms, p=0,05), Pmax decreased (111,9 +/- 9,1 ms to 104,0 +/- 12,4 ms, p=0,003) and P-wave dispersion decreased (62,5 +/- 10,6 ms to 51,3 +/- 8,9 ms, p<0,001) with nebivolol, Pmin increased (44,4 +/- 9,8 ms to 58,0 +/- 15,5 ms, p=0,02), Pmax didn't change (106,1 +/- 13,8 ms to 107,0 +/- 11,6 ms, p=NS) and P-wave dispersion decreased (61,7 +/- 15,0 ms to 49,0 +/- 13,7 ms, p<0.001) with atenolol. However, there was no statistical difference between pre- and post-treatment values of two groups. Conclusions. Both nebivolol and atenolol are effective in improvement of P-wave dispersion in patients with hypertension and there's no significant difference between them.