INTRODUCTION: The effects of combustible cigarettes (CCs) and electronic nicotine delivery systems (ENDS) on immune cell-driven colon inflammation and intestinal healing of patients with ulcerative colitis (UC) are still unknown and, therefore, were examined in this study. AIMS AND METHODS: Intracellular staining and flow cytometry analysis of immune cells isolated from UC patients who used ENDS (UCENDS), CCs (UCCC) and who were nonsmokers (UCAIR) were performed to elucidate cellular mechanisms which were responsible for CCs and ENDS-dependent modulation of immune response during UC progression. Additionally, dextran sulfate sodium (DSS)-colitis was induced in ENDS/CC/air-exposed mice (DSSENDS/ DSSCC/DSSAIR groups) to support clinical findings. RESULTS: Significantly increased number of immunosuppressive, IL-10, TGF-β, and IL-35-producing, FoxP3-expressing CD3 + CD4 + T regulatory cells (Tregs) was observed in the blood of UCENDS patients while the reduced presence of inflammatory, TNF-α and IFN-γ-producing, Tbx21-expressing CD3 + CD4 + Th1, IL-4-producing Gata3-expresing Th2 and IL-17, IL-22-producing, RORγT, IL-23R-expressing Th17 cells were noticed in the blood of UCCC patients. Exposure to either CCs or ENDS was associated with enhanced mucosal healing, ameliorated spontaneous recovery, and improved survival of DSS-treated mice. An expansion of immunosuppressive cells (IL-10-producing tolerogenic CD11c + dendritic cells, alternatively activated CD206, Arginase 1-expressing, IL-10-producing F4/80 + macrophages, IL-10-producing FoxP3-expressing Tregs) was noticed in the colons of DSSENDS-treated mice, while reduced number of inflammatory, IL-17- and IL-4-producing T lymphocytes was observed in the colons of DSSCC-compared to DSSAIR-treated mice. CONCLUSIONS: Despite different mechanisms of action, both ENDS and CCs attenuated ongoing colon inflammation, enhanced healing, and ameliorated recovery of injured intestines of DSS-treated mice and UC patients. IMPLICATIONS: This is the first study that compared the effects of CCs and ENDS on immune cells of patients suffering from UC, providing new information about molecular and cellular mechanisms which were responsible for ENDS and CCs-dependent modulation of immune cell-driven colon injury and inflammation. Obtained results showed that both ENDS and CCs had the capacity to attenuate detrimental immune response, enhance healing, and ameliorate recovery of injured intestines.