Chronic and persistent lung infections cause the majority of morbidity and mortality in cystic fibrosis patients. Galactosyl ceramide has been previously shown to be involved in Pseudomonas internalization. Therefore, we assessed ceramide levels in the plasma of CF patients and compared them to healthy volunteers using HPLC followed by Mass Spectrometry. Our results demonstrate that CF patients display significantly lower levels of several ceramide sphingolipid species, specifically C14:0, C20:1, C22:0, C22:1, C24:0 ceramides and dihydroxy ceramide (DHC16:0). We report that Cftr knockout mice display diminished ceramide levels in CF related organs (lung, pancreas, ileum and plasma) compared to their littermate controls. Since it has been previously reported that in vitro treatment with fenretinide induced ceramide in neuroblastoma cell lines, we decided to test this drug in vivo using our Cftr knockout mice in attempt to correct this newly identified defect in ceramide levels. We demonstrate that treatment with fenretinide is able to increase ceramide concentrations in CF related organs. We further assessed the biological effect of fenretinide on the ability of Cftr knockout mice to combat lung infection with P. aeruginosa. Our data show dramatic improvement in the ability of Cftr knockout mice to control P. aeruginosa infection. Overall, these findings not only document a novel deficiency in several ceramide species in CF patients but also demonstrate a pharmacological mean to correct this defect in Cftr-knockout mice. Our data provides a strong rationale for clinical intervention that may benefit cystic fibrosis patients suffering from CF lung disease.