Objective To explore the clinical significance of adenosine deaminase (ADA)in pleural effusion for diagnosis of tuberculosis pleuritis in children. Methods The level of ADA in pleural effusion was retrospectively analyzed in 28 cases with purulent pleuritis, thirty-four cases with mycoplasma pneumoniae pleuritis, forty-five cases with tuberculosis pleuritis from July 2011 to January 2014 in Beijing Children's Hospital Affiliated to Capital Medical University. Results The level of ADA in three groups was expressed by median (range interquartile). ADA in the purulent pleuritis group [126.35 (76.80, 178.13)U/L]was higher than the group of mycoplasma pneumoniae pleuritis[55.55 (42.80, 79.03)U/L]and tuberculosis pleuritis[26.50 (22.05, 50.95)U/L]. The difference was statistically significant (P< 0.01). The cut-off value of pleural effusion ADA for diagnosis of tuberculosis pleuritis is not available by application of ROC curve. Conclusion Higher ADA value is not only the characteristic of tuberculosis pleuritis, but also purulent pleuritis and mycoplasma pneumoniae pleuritis.ADA has no clinical value in diagnosis of tuberculosis pleuritis in children. Key words: Adenosine deaminase; Pleural effusion; Children; Diagnosis; Tuberculosis pleuritis