No report has been found comparing Chlamydia pneumoniae (C. pneumoniae) pneumonia radiographically with other atypical pneumonias, Chlamydia psittaci (C. psittaci) pneumonia and Mycoplasma pneumoniae (M. pneumoniae) pneumonia. We described the chest radiographs of three kinds of pneumonia cases: 46 cases of C. pneumoniae pneumonia, 39 cases of C. psittaci pneumonia, and 131 cases of M. pneumoniae pneumonia. Radiographic shadows were categorized into main shadows and sub-shadows. The main shadows are classified from the viewpoint of the characteristics; air space consolidation(AS), ground-glass opacity(GG), reticular shadow(RS), bronchopneumonia(BP), and small nodular shadows (SN). The size, the site, and the number of the main shadows were also analyzed. In comparison among the three pneumonias, BP was the most frequent in M. pneumoniae pneumonia (0.40/case). AS predominated in C. pneumoniae pneumonia (0.67/case), and GG in C. psittaci pneumonia (0.62/case). The number of main shadows was equal, about 1.4/case in three pneumonias. Large shadows were less frequent in M. pneumoniae pneumonia than C. pneumoniae pneumonia (p = 0.02) and C. psittaci pneumonia (p = 0.01). Main shadows were more frequent in the outer zone in M. pneumoniae pneumonia than C. psittaci pneumonia (p = 0.01), and in the middle zone in C. psittaci pneumonia than in M. pneumoniae pneumonia (p = 0.02). Cases with bilateral main shadows were less common in M. pneumoniae pneumonia (9%) than C. pneumoniae pneumonia(33%, p = 0.001) and C. psittaci pneumonia(30%, p = 0.005). Thickening of bronchovascular bundles as a sub-shadow was most frequently noted in M. pneumoniae pneumonia. Some differences among the three atypical pneumonias were seen in the chest radiograph. However, no specific findings of C. pneumoniae pneumonia were shown radiographically in this study.