The aim of this study was to investigate the diagnostic usefulness and clinical values of the sonographic feature of peripheral hypoechoic spaces (PHES) in children with necrotizing pneumonia (NP). Between July 2002 and July 2004, 23 consecutive children with NP in whom we performed real-time chest ultrasound were enrolled into our study. Details of demographics, clinical characteristics, laboratory data, causative pathogens, complications and outcomes of these children were recorded and analyzed. PHES in ultrasonography (US) were defined as peripheral cavitations seen as hypoechoic areas in consolidated lung. The sonographic feature of PHES was correlated with the diagnosis of NP and was also used to correlate with the clinical characteristics, complications and outcomes in children with NP. Sensitivity, specificity, and positive predictive value of this sonographic finding for the diagnosis of NP were 35%, 100%, and 100%, respectively. Pneumothorax was seen more commonly in children who presented PHES in US, with a significant difference (p < 0.05). In conclusion, the sonographic feature of PHES appears to be more specific for detecting NP in childhood pneumonia. In children with pneumonia with PHES in consolidated lung, the diagnosis of NP can be suggested with confidence, and it is important to be aware of the life-threatening complication of pneumothorax to decrease morbidity.