The diagnosis of neonatal atelectasis (NA) is usually based on clinical manifestations and chest X-rays, lung ultrasounds are not included in the diagnostic work-up of NA.Recently, ultrasounds have been used extensively and successfully in the diagnosis of many kinds of lung diseases, but few studies have addressed NA. The aim of this study was to evaluate the ultrasound imaging features of NA-and to evaluate the value of lung ultrasound in diagnosing NA. From May, 2012 to June, 2013, 40 newborn infants with NA and another 40 neonates without lung disease were enrolled into this study.Lung ultrasound was performed at the bedside by a single expert physician.In a quiet state, the infants were positioned in supine, side or prone postures. The lung field was divided into three areas by the anterior auxilary and posterior auxilary line. The regions of the bilateral lungs were scanned by the probe which was vertical or parallel with the ribs, then compared the results with conventional chest X-ray findings. (1) The main ultrasound imaging features of neonatal NA include lung consolidation with air bronchograms, pleural line abnormalities and A-line disappearance. Besides, lung pulse and lung sliding disappearance could be seen by real-time ultrasound. (2) The sensitivity of lung ultrasound for diagnosis of NA was 100%, while it was only 70% for conventional chest X-rays. Use of ultrasound to diagnose NA is accurate and reliable, the sensitivity was superior to that of conventional chest X-ray examination, which also has many other advantages including easy-operating, non-ionizing, can be performed at the bedside, therefore, ultrasonic can provide important value for clinicians.