Individuals with asthma experience a rapid deterioration in their lung function, this is understood to be connected to elements of airway inflammation and/or remodeling. Purpose: To evaluate the relation between CD8 levels and the severity of bronchial asthma, as well as to analyze the discriminative performance of CD8 in distinguishing between asthma cases that are under control and those that are not. Methods: This case-control study included 120 asthmatic individuals and 120 non-asthmatic controls. The diagnosis of asthma was accomplished in accordance with GINA. The spirometry test, total and differential leucocytic count, and the CD8 level calculation were performed for each study participant. Results: - CD8 (%) showed a significant variance between mild, moderate and severe persistent cases (p-value less than 0.001). CD8 (%) was elevated in uncontrolled patients in contrast to partially controlled and well controlled individuals. A significant positive correlation between CD8 and Eosinophils % (p-value = 0.002) (r = 0.84), as well as eosinophils in sputum (p-value less than 0.001) (r = 0.94). Conversely, a significant negative correlation was observed between CD8 and the FEV1 (p-value less than 0.001) (r = -0.66) and TLC (p-value less than 0.001) (r = -0.77) and FEV1/FVC (p-value less than 0.001) (r =-0.81) among the asthmatic group. Conclusion: Both the severity of asthma and level of control were associated with CD8%. Moreover, CD8 cells may predict the course of asthma, which implies that preventing the faster deterioration of lung function in asthmatic patients may need focusing on certain aspects of inflammation.