Abstract: Objective To investigate the relationship between peripheral blood mononuclear cells (PBMC) and tuberculosis. Methods 150 tuberculosis patients (tuberculosis group), 80 lung cancer patients (lung cancer group) and 100 healthy volunteers (control group) screened from the Fourth People's Hospital of Taiyuan between January 2013 and December 2016 were included in the present study. The tuberculosis group was divided into the initially treated young subgroup, initially treated old subgroup and retreated young subgroup. The percentage of PBMC in the tuberculosis group and the lung cancer group when admitted to hospital and that in the control group form physical examination record were collected and compared. Results Significant difference in PBMC percentage among the three group was detected (F=67.59, P<0.05). The PBMC percentage in the tuberculosis group was (10.8±2.94)%, which was higher than that in the control group (6.86 ± 1.42)% and the lung cancer group (7.95 ± 1.73)% (P<0.05). The PBMC percentage in the initially treated young subgroup, initially treated old subgroup and retreated young subgroup was (10.80±2.72)%, (10.40 ± 2.82)% and (10.52 ± 3.22)%; but there was no statistically significant difference (F = 0.22, P = 0.804). Conclusion The percentage of PBMC in patients with pulmonary tuberculosis was increased.