Aims: Left atrial thrombosis (LAT) is usually detected by transesophageal echocardi- ography (TEE). The aim of the present study was to identify clinical and echocardio- graphic factors associated with left atrial thrombosis in atrial fibrillation (AF) patients undergoing early electrical cardioversion (ECV) in order to create scores that can predict LAT, in a non-invasive way. Methods: A consecutive cohort of patients with persistent AF scheduled for ECV was evaluated by transthoracic echocardiography and TEE. By a logistic regression model, variables significantly associated with LAT were assessed and introduced in predictive models to develop both a clinical and an echocardiographic prediction score for the presence of LAT. Results: In total, 125 patients [median 71 (range 49-88) years, 60.0% males] were enrolled. Transesophageal echocardiography showed LAT in 35 patients (28%). The clinical variables significantly associated with LAT were previous stroke (OR = 4.17), higher CHA2DS2-VASc score (OR = 1.93), lower estimated glomerular filtration rate (OR = 0.80), and higher brain natriuretic peptide levels (OR = 1.44). Among echocar- diographic parameters, E/e′ ratio was directly associated with LAT (OR = 2.25), while an inverse correlation was detected with left ventricular ejection fraction (OR = 0.43) and total global left atrial strain (OR = 0.59). Two prediction scores (clinical and echo- cardiographic) were developed. The positive predictive values of the clinical and the echocardiographic score were 80% and 100%, respectively, while the negative pre- dictive values were 98% and 94%, respectively. Combined use of the scores reached a positive and negative predictive value of 100%. Conclusions: When providing concordant information the two scores are able to cor- rectly identify patients with or without LAT. An external validation is necessary to demonstrate their usefulness in the clinical practice.