OBJECTIVE: To study the characteristics of the chest X-ray images in children infected with enterovirus 71. MethodsA total of 120 children with enterovirus 71 infection between April, 2010 and July, 2011 were classified into three groups according to the disease condition: mild (31 cases), severe (43 cases) and life-threatening (46 cases). The period from the onset of clinical symptoms to the first chest X-ray imaging examination and the results of the first chest X-ray findings were compared among the three groups. RESULTS: The period from the onset of clinical symptoms to the first chest X-ray imaging examination in the mild, severe and life-threatening groups was 26- 48 hrs (median 37 hrs), 10-36 h (median 23 hrs) and 2-36 hrs (median 19 hrs) respectively. Chest X-ray abnormalities were initially observed at 30 hrs after the onset of clinical symptoms in the mild group, at 23 hrs in the severe group and at 2 hrs in the life-threatening group (P<0.01). The mild group presented an initial imaging abnormality rate of 5.8%, the severe group 81.3% and the life-threatening group 100%. The life-threatening group showed a significantly higher initial X-ray abnormality rate than the other two groups (P<0.01). In terms of chest X-ray performance, the mild group usually presented lung marking thickening or vagueness. Most children in the severe group presented lung effusion and consolidation. Signs of pulmonary edema were found in the life-threatening group, and lesions in the life-threatening group were characterized by wide distribution and many lung lobe involvements. CONCLUSIONS: The interval between the onset of clinical symptoms and the initial chest X-ray examination, the period of time of, and the onset of clinical symptoms, at which chest X-ray abnormalities, the abnormality rate and the severity of chest X-ray findings may be paralleled to the clinical situation in children with enterovirus 71 infection.