The aim of the study was to evaluate the importance of time and frequency domain analysis of P-wave signal averaging, left atrium size measured echocardiographically and time of P.-wave assessed in II lead of standard ECG in patients with different frequency of atrial fibrillation events. The material consisted of 110 pts (81 men and 29 women), mean age 60.44 +/- 10.73 with atrial fibrillation events concomitant coronary heart disease and/or primary hypertension documented in standard ECG or Holter monitoring. The positive correlation, statistically significant between the frequency of atrial fibrillation events and the time of filtered P-wave vector, the time of filtered P-wave in X, Y, Z leads and differences between times of filtered P-wave vector and times of P-wave in II ECG lead was confirmed. Additionally the negative correlation, statistically significant between frequency of atrial fibrillation events and RMS10, RMS20 and RMS30 was confirmed. There was no correlation between frequency analysis of P-wave averaging or left size and frequency of atrial fibrillation events.