Background: As Mycoplasma pneumoniae pneumonia has increased in Korea, its relevance to infants, toddlers, and adolescents has magnified as well as. However, it is difficult to perform the serological test and PCR test routinely for diagnosis in actual clinical practice. Thus, the authors conducted this study to help clinicians do presumptive diagnosis of Mycoplasma pneumoniae pneumonia using clinical, radiological, and hematological findings. Methods: The study population consisted of 224 children between 1 month and 14 years old, hospitalized for radiographically confirmed pneumonia. Patients were divided into two groups of 100 children with Mycoplasma pneumoniae pneumonia, as diagnosed using the ELISA method. Groups with negative result in Mycoplasma IgM antibody test were classified into the viral group (98 patients with respiratory virus) and the bacterial group (46 patients with the bacteria detected in the blood sputum culture or antibiotic treatment except macrolide improved the patient`s condition). These groups were compared and analyzed using clinical, hematological,and radiographic differences and scoring system. Results: Clinical, hematological, and radiographic characteristics of Mycoplasma pneumoniae pneumonia have shown the intermediate level results between bacterial pneumonia and viral pneumonia. In terms of scoring system, the mean score of Mycoplasma pneumoniae pneumonia was 4.23, which was the intermediate level between bacterial pneumonia (mean score=6.67) and viral pneumonia (mean score=1.48). Conclusion: Results suggest that the combination of the scoring system information can increase the accuracy in the diagnosis even if they may have difficulties on diagnosis, because clinical manifestations, hematological, and radiographic findings are nonspecific.