We aimed to test the hypothesis that a lung ultrasound severity score (LUS) and assessment of left ventricular eccentricity index of the interventricular septum (LVEI) by focused heart ultrasound can predict extubation success in mechanically ventilated infants. We conducted a prospective study on premature infants <34 weeks’ of gestation. LUS was performed on postnatal days 3 and 7 by an investigator who was masked to infants’ ventilator parameters. LVEI and pulmonary artery pressure (PAP) were measured at postnatal day 3. A receiver operator curve was constructed to assess the ability to predict extubation success. Spearman correlation was performed between LVEI and PAP. A total of 104 studies were performed to 66 infants; of them 39 had mild and 65 had moderate-severe lung disease. LUS predicted extubation success with a sensitivity and a specificity of 91% and 69%, respectively. Area under the curve was 0.83 (CI: 0.75-0.91). LVEI did not differ between infants that succeeded and failed extubation. It correlated with PAP during systole (r=0.66). We conclude that LUS predicts extubation success in mechanically ventilated preterm infants whereas LVEI correlates with high PAP.