A B S T R A C T Background: CD26 is expressed in all chronic myeloid leukemia (CML) patients. This study investigated the role of CD26+ LSCs in diagnosis and follow up of CML patients. Method: Flow cytometry was performed to evaluate CD26+ LSC in peripheral blood (PB) in CML patients. BCRABL1 transcript level measurement was performed using standard qRT-PCR technique. Results: CD26+ LSCs were significantly correlated with BCR-ABL1 transcript level at diagnosis and after three months of treatment. CD26+ LSCs also were significantly associated with the risk score after 12 months of treatment. Conclusion: CD26+ LSCs can be a useful marker in diagnosis and follow up of patients with CML.