The objective of this study was to assess the computed tomography (CT) features of Mycoplasma pneumoniae pneumonia. We retrospectively reviewed CT findings of 16 patients (M:F = 9:7, age range 1-74 years, median 9 years) with serologically proven Mycoplasma pneumoniae pneumonia and with chest CT scan available. Two distinctive patterns of CT features of M. pneumoniae pneumonia were noted between the paediatric (age < 18 years) and the adult (age > or = 18 years) groups. The pediatric group (n=11) showed lobar or segmental consolidation (100%) with frequent pleural effusion (82%) and regional lymphadenopathy (82%) and mild volume decrease of the involved lobe (73%), while four of the five adult patients showed diffuse and/or multifocal, centrilobular or peribronchovascular areas of ground-glass attenuation (80%) with a lobular distribution, and frequent thickening of interlobular septa (60%) and the bronchial walls (40%) were also detected at high-resolution CT. The CT finding of a lobar or segmental consolidation with a parapneumonic effusion seen in our children with M. pneumoniae pneumonia was similar to that of bacterial lobar pneumonia. In contrast, the CT findings noted in our adult patients consisted of a mixture of a bacterial bronchopneumonia pattern and a viral interstitial pneumonia pattern.