Objective Assess the earliest time of LUS to guide surfactant therapy. Study design In this observational study (ClinicalTrials.gov Identifier NCT04544514), LUS was performed within 30 min and repeated at 1, 2, 4, and 6 h on preterm babies. White lung appearance was defined as type 1 group, whereas prevalence of lines B as type 2 and lines A as type 3. Ultrasound and radiographic findings were also compared to determine surfactant need. Results Among 71 patients, 41 received surfactant therapy. In the first evaluation, 37 of them have been defined as type 1, whereas 4 of them have been as type 2 group. Type 3 group did not receive surfactant. Type 1 findings were superior to predict surfactant need and the predictive value was 100% at 2 h. Conclusion Even early LUS assessment at the first 20-30 min was more significant to predict surfactant need than x-ray. Presence of white lung appearance for 2 h indicates an absolute surfactant need.