Impaired phagocytosis of Pseudomonas aeruginosa was found in isolated monocytes of peripheral blood of cystic fibrosis patients, but not in their neutrophils, as reported some years ago. In the present study, we analysed the phagocytic capacity of peripheral blood neutrophils and monocytes of cystic fibrosis patients and of healthy controls. Phagocytosis was determined using a commercial phagocytosis “in whole blood” assay on the basis of fluorescence-labelled opsonized Escherichia coli bacteria and flow cytometry. Venous blood of cystic fibrosis patients and of healthy controls was collected and the phagocytosis assay was performed. No differences in the percentage of phagocytic cells or in the overall phagocytic capacity were found between samples of cystic fibrosis patients and healthy controls either in monocytes or in neutrophils. Thus, our results did not support the hypothesis of a generally reduced phagocytic ability in the peripheral blood immune cells of cystic fibrosis patients.