Objective To explore the reliability and accuracy of lung ultrasound for diagnosing neonatal pneumothorax. Methods This study was divided into two phases. (1) In the first phase, from January 2013 to June 2015, 40 patients with confirmed pneumothorax had lung ultrasound examinations performed to identify the sonographic characteristics of neonatal pneumothorax. (2) In the second phase, from July 2015 to August 2016, lung ultrasound was undertaken on 50 newborn infants with severe lung disease who were suspected of having pneumothorax, to evaluate the sonographic accuracy and reliability to diagnose pneumothorax. Results (1) The main ultrasonic manifestations of pneumothorax are as follows: ① lung sliding disappearance, which was observed in all patients (100%); ② the existence of the pleural line and the A-line, which was also observed in all patients (100%); ③ the lung point, which was found in 75% of the infants with mild-moderate pneumothorax but not found to exist in 25% of the severe pneumothorax patients; ④ the absence of B-lines in the area of the pneumothorax (100% of the pneumothorax patients); and ⑤ no lung consolidation existed in the area of the pneumothorax (100% of the pneumothorax patients). (2) The accuracy and reliability of the lung sonographic signs of lung sliding disappearance as well as the existence of the pleural line and the A-line in diagnosing pneumothorax were as follows: 100% sensitivity, 100% specificity, 100% positive predictive value, and 100% negative predictive value. When the lung point exists, the diagnosis is mild-moderate pneumothorax, whereas if no lung point exists, the diagnosis is severe pneumothorax. Conclusion Lung ultrasound is accurate and reliable in diagnosing and ruling out neonatal pneumothorax and, in our study, was found to be as accurate as chest X-ray. © 2017 Elsevier Inc.