Pentraxin-3 (PTX3) is a member of the long pentraxin superfamily and has a nonredundant role in mediating resistance to fungal pathogens. Serial monitoring of PTX3 plasmatic levels was performed in 10 pediatric leukemia patients affected by pulmonary fungal infections. When compared with values of a control pediatric cohort, PTX3 showed significantly higher plasmatic values. Moreover, the response to the antifungal therapy correlated with normalization of PTX3 values. PTX3 may represent a useful tool for the diagnosis and monitoring of fungal infections in immuno-compromised children.