Objective: The aim of this study was to evaluate the value of lung ultrasound in the diagnosis of respiratory distress syndrome (RDS) in newborn infants. Methods: From March 2012 to May 2013, 100 newborn infants were divided into two groups: RDS group (50 cases) and control group (50 cases). According to the findings of chest x-ray, there were 10 cases of grade II RDS, 15 grade III cases, and 25 grade IV cases in RDS group. Lung ultrasound was performed at bedside by a single expert. The ultrasound indexes observed in this study included pleural line, A-line, B-line, lung consolidation, air bronchograms, bilateral white lung, interstitial syndrome, lung sliding, lung pulse etc. Findings: In all of the infants with RDS, lung ultrasound consistently showed generalized consolidation with air bronchograms, bilateral white lung or interstitial syndrome, pleural line abnormalities, A-line disappearance, pleural effusion, lung pulse, etc. The simultaneous demonstration of lung consolidation, pleural line abnormalities and bilateral white lung, or lung consolidation, pleural line abnormalities and A-line disappearance co-exists with a sensitivity and specificity of 100% for the diagnosis of neonatal RDS. Conclusion: This study indicates that using an ultrasound to diagnose neonatal RDS is accurate and reliable tool. A lung ultrasound has many advantages over other techniques. Ultrasound is non-ionizing, low-cost, easy to operate, and can be performed at bedside, making this technique ideal for use in NICU. © 2014 by Pediatrics Center of Excellence, Children's Medical Center, Tehran University of Medical Sciences, All rights reserved.