Galactomannan (GM) is a major aspergilli cell-wall constituent released into circulation during the early stage of invasive disease, and can be detected. Many studies suggest that serum galactomannan assay has an excellent sensitivity and specificity for the early diagnosis of adult invasive aspergillosis (IA). However, there have been few studies on serum galactomannan assay in pediatric patients. Therefore, we evaluate the value of serum galactomannan assay in the diagnosis of pediatric invasive pulmonary aspergillosis in this study. Blood samples were obtained from 88 children, of whom 14 had definitive or possible invasive pulmonary aspergillosis (IPA), 16 had other invasive pulmonary fungal infection and 58 had pulmonary non-fungal infection. Of the 58 patients, 23 had bacterial pneumonia, 20 had mycoplasma pneumonia and 15 had pulmonary tuberculosis. A double-direct sandwich ELISA was employed to detect GM optical density index (ODI) in the serum sample. GM ODI were observed before and after treatment in six children with IPA. Measurement data followed the Gaussian distribution were expressed as x(-) +/- s; differences among groups were tested using a single factor analysis of variance. If the s>1/3 x(-), measurement data were expressed as M [minimum, maximum], and the differences among groups were tested by a rank sum test. P < 0.05 was considered to be statistically significant. The serum GM ODI in IPA group [1.03 (0.16 - 3.73)] was significantly higher than that in the other invasive pulmonary fungal infection group [0.30 (0.04 - 1.28)] and pulmonary non-fungal infection group [0.24 (0.08 - 0.69)] (P < 0.05). If the cut-off GM ODI was set at 0.5, the sensitivity and specificity of the assay for IPA were 71.4% and 91.9% respectively. The accuracy rate for IPA was 88.6%. If the cut-off GM ODI was set at 0.8, the sensitivity, specificity and accuracy rate for IPA were 64.2%, 98.6% and 93.2% respectively. Of 6 children whose GM were observed serially, GM ODI declined consistently with the clinical remission in 3 children. GM ODI raised in 2 children corresponding to clinical exacerbation. Whereas GM ODI elevated paradoxically regardless of clinical remission in the remaining one patient. Serum GM detection was an effective method for the diagnosis of pediatric IPA.