Abstract Funding Acknowledgements Type of funding sources: None. Background The restoration of sinus rhythm (SR) improves the mechanical function of the heart. Purpose To assess left atrial (LA) function before and within 24 hours after successful electrical cardioversion (EC) and its prognostic value for atrial fibrillation (AF) recurrence during 24 months follow-up. Methods Prospective study involved 71 patients with non-valvular AF (mean age 64 ± 13 years, 61% male). All patients underwent echocardiography before and after EC. We analysed standard parameters in two-dimensional echo, pulse-wave Doppler and tissue Doppler echocardiography. Using speckle-tracking method we assessed peak atrial longitudinal strain (PALS) and peak atrial contraction strain (PACS). Results During follow-up we noticed AF recurrence in 48 (68%) patients. Median time to AF recurrence was 2.4 (IQR 1 to 6.9) months. Left ventricular ejection fraction as well as E/E’ and PALS assessed during AF were statistically insignificant as potential predictors in univariate regression model. Receiver operating characteristic curve analysis revealed that left atrial volume index >37 ml/m² (AUC = 0.811, p < 0.0001), E/A ratio >2.1 (AUC = 0.828, p < 0.0001), A wave ≤0.4 m/s (AUC = 0.662, p = 0.01), mean E/E’ ratio during sinus rhythm >8.5 (AUC = 0.815, p < 0.0001), mean A’ wave of ≤5.5 cm/s (AUC = 0.848, p < 0.0001), PALS-SR ≤14.1% (AUC = 0.767, p < 0.0001), PACS ≤4.3% (AUC = 0.883, p < 0.0001) were the optimal cut-off values for predicting AF recurrence. Conclusions The assessment of LA and diastolic function conducted within 24 hours after successful cardioversion predicts long-term maintenance of sinus rhythm.