Background The role of particular immune checkpoints in the induction of systemic immunosuppression, which severely complicates the clinical course and prognosis in multiple myeloma (MM), is still unresolved. Only a subset of MM patients treated with checkpoint inhibitors derive benefits, suggesting differential participation of relevant receptors in the inhibitory signaling pathway. This study was undertaken to identify an immune checkpoint playing a key role in systemic T-cell-related immune deficiency in MM in the context of Th1/Th17/Treg cell distribution.Methods We used flow cytometry assay to examine the expression of PD-1, BTLA, and CTLA-4 in peripheral blood (PB) CD4 + , CD4 + CD127 + (Teff), and CD4 + CD127 - (Treg) T cell subsets as well as the balance of Th1/Th17/Treg cells. The study group consisted of 40 untreated (newly diagnosed or relapsed/refractory) myeloma patients in different clinical stages. The obtained results were compared to those observed in 20 healthy controls.Results Among immune checkpoints studied, only PD-1 was expressed on a significantly increased proportion of circulating Teff and Treg cells in MM; we also noted a positive correlation of PD-1 expression with clinical stage. Furthermore, the percentage of PD-1 + Teff cells was correlated with beta2-microglobulin serum concentration and shorter overall survival (OS). We also found higher Th17 and Treg compartments in PB irrespectively of tumor stage; however, in some studied subsets, a decrease at stage III was observed. Moreover, PB Th1 deficit (more pronounced in advanced disease) was also observed. Except for the PD-1 + Teff subset, none of the examined cell population was related to OS.Conclusions The study indicates that PD-1 expression on circulating T cell subsets may contribute to the imbalance in PB Th1/Th17/Treg cell distribution and systemic immunosuppression in MM. PD-1 seems to be the only immune checkpoint determining clinical behavior of patients, thereby strengthening the therapeutic potential for inhibitors.