OBJECTIVE To evaluate the impact of radiofrequency catheter ablation on left atrial (LA) size and function in patients with paroxysmal atrial fibrillation (PAF) and whether there is any difference between segmental pulmonary vein ostial isolation (SPVI) and circumferential pulmonary vein ablation (CPVA). METHODS Sixty-six patients with highly symptomatic atrial fibrillation were assigned to undergo either SPVI or CPVA. Transthorax echocardiography was performed before, 1 day, 1 months and 3 months after the procedure. LA dimension, LA area, late diastolic peak velocity of mitral valve inflow (A) and peak atrial systolic mitral annulus velocity (A') were recorded. RESULTS Of 66 consecutive patients with symptomatic PAF, 30 patients underwent SPVI and 36 underwent CPVA. After a mean follow-up of (315 +/- 153) days, 21 patients (70%) after SPVI and 28 patients (75%) after CPVA were free of atrial tachyarrhythmia. As compared with the baseline, LA area decreased at 1-month after ablation in SPVI group and at 3-month in CPVA group. LA dimension decreased also in SPVI group, but did not in CPVA group. A velocity and A' velocity declined remarkably 1 day after CPVA, and restored 3 months later. The former went back to the level of baseline, and the latter exceeded it apparently. In SPVI group, A velocity increased at 1-month, and maintained in 3-month after ablation. A' velocity increased at 3-month after ablation. No reduction of A velocity or A' velocity was found after SPVI. CONCLUSIONS This study demonstrated a decrease in LA area and an improvement in LA systolic function 3 months after ablation for PAF. The LA damage by CPVA was more than that by SPVI, which was characterized by the reduction of LA function 1 day after procedure and the delayed improvement of LA size and functional parameters.