BACKGROUND: The purpose of this study was to determine the prevalence of pulmonary dysfunction in pediatric hematopoietic cell transplant (HCT) survivors and to identify associated risk factors. PROCEDURE: In a cross-sectional study, patients surviving at least 5 years after pediatric HCT were requested to undergo pulmonary function testing (PFT). Risk factors for restrictive lung disease (RLD) and obstructive lung disease (OLD) were analyzed using multivariate analysis. RESULTS: Among 472 patients contacted, 260 (55%) participated and 215 were selected for analysis. These patients were transplanted at a median age of 8.3 (0.3-18.0) years; 175 for hematologic malignancies and 40 for non-malignant diseases. The preparative regimens for 133 patients included fractionated TBI (FTBI), 29 single-fraction TBI (SFTBI), and 53 non-TBI regimens. PFT was performed at a median of 10 (5.0-27.5) years after HCT. Forty percent of patients had either RLD or OLD (28% RLD, 9% OLD, 3% mixed RLD/OLD) and at least 15% had an isolated low-DLCO. Moderate-to-severe impairment was present in 45% of patients with RLD or OLD. In multivariate analysis, risk factors associated with RLD included transplant regimen, transplant diagnosis, scleroderma/contracture, and donor relation. Patients treated with SFTBI had the highest risk of RLD. Risk factors for OLD included chronic graft-versus-host disease, transplant regimen, and time after HCT. Patients surviving 20 or more years after HCT had the highest risk of OLD. CONCLUSIONS: Fifty-five percent of long-term pediatric HCT survivors had pulmonary dysfunction. These findings stress the need for long-term follow-up to detect pulmonary dysfunction. Copyright (c) 2005 Wiley-Liss, Inc.