Objective: Although mortality and morbidity due to community-ac quired pneumonia (CAP) decrease in childhood, parapneumonic effu sion (PE) and empyema still emerge as an important problem. There aremany studies related to platelet count and mean platelet volüme (MPV)in CAP together with many inflammatory markers. In this study, theneed for fibrinolytic therapy (FT) and its relationship with thrombocytecount and MPV in patients with CAP+PE was investigated. Material and Methods: This retrospective study was conducted by in cluding patients who were hospitalized and followed up with the diagno sis of CAP and PE between 2010 and 2017 in Clinic of Pediatric Infection,Gazi University Faculty of Medicine Hospital. Results: Forty-one patients with the diagnosis of CAP+PE were includedin the study. 46.3% of the patients were female and 53.7% were male. Me dian age was 72 months (2.5-192 months), median hospital stay was 14days (2-26). Fibrinolytic therapy was applied to 19 of the patients (43.9%).Of the patients recieved who received FT, 13 (68.4%) received urokinase, 5(26.3%) streptokinase, and 1 alteplase (5.2%). The hospitalization period ofpatients who received FT, was significantly longer (p= 0.001), and the leu kocyte count and CRP levels on the day of hospitalization were significantlyhigher than those who did not (p= 0.009, p= 0.001). While there was nodifference in CRP and leukocyte values on the day of discharge betweenthe patients who received FT and those who did not; on the day of dis charge, the platelet value was found to be significantly higher in patientswho received FT compared to patients who did not (p= 0.02). In 77.8% ofpatients who received FT, the highest platelet value was observed after 10.day of hospitalisation whereas 69.9% of the patients who did not receive FTreached the highest platelet count in the first 10 days (p= 0.006). Conclusion: The significantly higher CRP and white blood cell values inpneumonia and parapneumonic effusion patients who received fibrino lytic therapy compared to those who did not receive FT may be attributedto the more severe inflammation in these patients. Besides the significantincrease in discharge platelet values may indicate that thrombocytosis isa late acute phase reactant. However, it may be important that the plate let count reaches the highest level after the 10th day in patients receiv ing FT, in terms of the possibility that this treatment may contribute tothrombocytosis