Purpose: This study was conducted to evaluate the prevalence, clinical characteristics and laboratory findings of lobar pneumonia in children caused by Mycoplasma pneumonia and to find a diagnostic tool for identifying M. pneumoniae infection in children. Methods : We analyzed medical records of 78 children between March 2010 and December 2011, who were admitted to our hospital and diagnosed with lobar pneumonia on the basis of chest X-rays. White blood cells (WBC), C-reactive protein (CRP), procalcitonin (PCT), specific antibodies to M. pneuomoniae, and cold agglutinin (CA) were measured at the time of admission. Children were divided into 2 groups: those with M. pneumoniae infection (group A) and those without infection (group B). Group A children were also subdivided into 2 categories: those with increased CA (group 1) and those without (group 2). Results: The prevalence of lobar pneumonia was higher in the year 2011 than in 2010. M. pneumonia infection usually occurs in summer and autumn. Group A children accounted for 75.6% (59/78) of all the cases. The onset ages was higher in group A than in group B (P =0.016). WBC counts and PCT values were higher in group B than in group A.(P =0.015 and P =0.011, respectively) Radiologic findings showed that the lower lobe was most commonly involved without predilection for either side and pleural effusion was present in 13.6% of all the cases. The duration of fever before admission was longer in group 1 than in group 2.(P =0.019) Conclusion : It is concluded that lobar pneumonia caused by M. pneumoniae can be more accurately diagnosed using serum PCT values than using CRP values.