Aim. To study the proportion of CD8+CD28+ and CD4+CD28+ cells among the CD8+ and CD4+ lymphocytes and the changes in these indicators in patients with HIV infection/tuberculosis (HIV/TB) versus those with HIV infection and those with TB. Subjects and methods. One hundred and six persons were examined and included into 4 study groups: 1) 39 patients with concomitant HIV/TB; 2) 25 patients with HIV monoinfection without TB who had not previously received antiretroviral therapy; 3) 17 patients with TB without HIV infection; 4) 25 healthy individuals (a control group). Results. CD28 expression was found to be much more reduced on the CD8 lymphocytes than that on the CD4 ones. This is likely to be due to earlier CD8 lymphocyte dysfunction in both the patients with HIV infection and those with HIV/TB although the CD4 cell is the basic virus target. Conclusion. The study of the proportion of CD8+CD28+ cells among the CD8 lymphocytes is of more informative value than the determination of that of CD4+CD28+ among the CD4 lymphocytes.