Objective: Pulmonary complications occur in 40-60% of patients undergoing HSCT, causing 10-40% of transplant-related deaths. Late-onset noninfectious pulmonary complications (LONIPCs) has been used for different entities occurring later than 3 months after transplant, such as idiopathic pneumonia (IP), bronchiolitis obliterans (BO) and bronchiolitis obliterans with organizing pneumonia (BOOP). The aim of this study was to analyze the incidence, risk factors and clinical outcome of LONIPCs in pediatric patients after HSCTs. Methods: We retrospectively evaluated 103 children who survived more than 3 months among the 120 patients who underwent HSCT for hematological malignancies (n=89) and non-malignant hematological diseases (n=31) at the Chonnam National University Hospital between Feb. 1995 and Dec. 2008. Logistic regression analysis was performed to investigate the influences of many factors, including patient age, sex, ABO incompatibility, disease status, graft source, HLA disparity, use of TBI, ATG, intensity of conditioning regimen, GVHD prophylaxis and the presence of GVHD on the onset of LONIPCs. Results: Among the 103 patients, 12 patients (11.7%) developed LONIPCs at a median interval of 340 days after HSCT (range, 95-1100 days). The patients with LONIPCs were subclassified into BOOP (n=6), BO (n=5), and IP (n=1). The presence of extensive chronic GVHD was significantly associated with the development of LONIPCs ( P=.001). Only 2 patients responded to treatment with steroid and immunosuppressive agents. Six of the 12 patients died. The 5 year OS rate in the patients with LONIPC was significantly lower than those without LONIPC (48.6% vs 70.8%, P=.049). Conclusion: Our results indicate that the development of LONIPCs was strongly associated with chronic GVHD. Early detection and prompt intervention may be most important to the patients with LONIPCs. Because of the poor prognosis despite aggressive treatment, novel and effective strategies aimed at the prevention and treatment of LONIPCs as well as chronic GvHD should be developed.