BACKGROUND: Myeloid-derived suppressor cells (MDSC) are categorized as granulocytic (G-MDSCs) and monocytic (M-MDSCs) and their expansion play a role in cancer progression. Recruitment to the cancer site depends upon the presence of a chemoattractant. We aimed to investigate the presence of MDSC subtypes and of interleukin-8 (CXCL-8) in the peripheral blood in lung cancer subtypes including non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) patients. MATERIALS AND METHODS: Peripheral blood samples of 26 NSCLC patients, 18 SCLC patients, and 8 healthy control donors (HDs) were harvested and the surface expression of CD14, CD15, CD11b, and HLA-DR on MDSCs was measured using flow cytometry. The level of serum CXCL8 was measured by the ELISA method. RESULTS: The frequency of circulating M-MDSCs was significantly higher in patients with NSCLC than in SCLC and HDs. In contrast, there was no statistical difference concerning the frequency of circulating G-MDSCs between the three groups. The concentration of CXCL-8 was significantly higher in the NSCLC and SCLC patients than in HD control with no significant difference between NSCLC and SCLC groups. There was no correlation between serum CXCL8 and G-MDSC levels. CONCLUSION: Our data confirm a higher frequency of circulating M-MDSCs, but not G-MDSCs, in the blood of those suffering from NSCLC but not for SCLC cases. Measuring MDSC subtypes and serum chemotactic factors may have implications for the differential diagnosis of NSCLC.