ABSTRACT. We investigated the effects of metastasis, surgery and chemotherapy on both circulating dendritic cells (DCs) and monocyte-derived-DCs (MoDCs) in colorectal cancer (CRC) patients. Metastatic or nonmetastatic CRC patients had significantly reduced DC subsets compared to healthy subjects (p<0.001). These cells were significantly higher in metastatic than in nonmetastatic patients. MoDCs were significantly lower in metastatic than healthy and nonmetastatic subjects (p<0.001). Surgically treated patients had nearly one-half circulating DC subsets compared to healthy subjects (p<0.001) while no difference was found between unoperated and healthy subjects. MoDCs obtained from tumor-bearing were significantly higher than in operated subjects. In both cases, MoDCs were significantly lower than in healthy subjects (p<0.001) Circulating DCs and MoDCs were significantly lower in CRC patients, with or without chemotherapy, compared to healthy subjects (p<0.001). Compared to untreated, chemotherapy- treated patients had 30% fewer DC subsets and lower MoDCs. Characterization of circulating DC subsets and MoDCs may elucidate CRC patients’ immune system status.