Aim: To clarify the epidemiological findings and characteristics of ground glass lesions on chest computed tomography (CT) after blunt trauma. Setting and Design: A medical college hospital and retrospective study. Materials and Methods: We retrospectively investigated all blunt chest trauma patients who were admitted from January 2004 to December 2010. The inclusion criteria were patients with: (1) chest CT examination on arrival, (2) intrathoracic traumatic lesions confirmed by initial CT, and (3) a second chest CT examination within 7 days from admission. We divided the subjects into two groups. A GG group included subjects who had ground glass lesions on initial chest CT and a control group included subjects who did not have the ground glass appearance. Results: The average age in the GG group was significantly lesser than that in the control group. The ratio of improvement for the value of SpO2/FiO2 between on arrival and the second hospital day and ratio of improvement for CT findings between on arrival and the second CT examination in the GG group was greater than in the control group. Conclusion: The ground glass appearance on chest CT after blunt trauma was not rare, and the patients with ground glass lesions were younger and tended to have a better improvement of oxygenation and CT images in comparison with the patients without these characteristic lesions.