Background: Chronic lymphocytic leukemia (CLL) is a monoclonal disorder characterized by uncontrolled proliferation of mature B lymphocytes. CD26 is a multi-functional type II cell surface glycoprotein, which is expressed mainly by T lymphocyte and it has a regulatory role in progression and also in migration and metastasis of tumour.   Objective: The aim of the work was to assess the regulatory role and expression of CD26 in patients with B-CLL and B-cell non-Hodgkin lymphoma (B-NHL) and the relation to disease staging and progression. Methods:  This study was conducted on 6 patients with B-CLL and 5 patients with NHL who were attending at National Cancer Institute. We detected functional role and specificity of CD26 by flow cytometry during the period from December 2019 to March 2020. The ages of patients ranged from 42 to 79 years old. Besides, 5 healthy individuals worked as control group. Results: A significant difference was found as regards expression of CD26 in CLL cases in comparison to control cases (p.0001). Also there was a significant difference between the NHL group and control group in expression of CD26 (p.0001). But no significant difference was detected between the NHL groups and CLL groups in expression of CD26 (p.052). Conclusion: This study confirmed that CD26 expression in CLL and NHL is variable and didn't correlate with other prognostic factors. In addition, there was no significant difference between the NHL groups and CLL groups in expression of CD26.