Flow cytometric methods are used to count leukocytes in quality control (QC) of blood components using the LeucoCount method. This involves using fluorescent dyes that bind to DNA/ RNA in combination with TruCount tubes. Flow cytometric can also be used to analyze lymphocyte subpopulations using the BD MultitestTM 6-color TBNK reagent and TruCount tubes. The study aimed to evaluate the stability of leukocyte counting QC samples and blood samples for lymphocyte subpopulation analysis within 48 hours of collection. In this study 10 erythrocytes concentrates, 10 thrombocytes concentrate, 10 blood doner samples and 14 patient samples was collected. The results showed that both the QC samples and patient samples can be stored for up to 48 hours without significant changes. Some variation was observed between the analysis conducted at 4, 24 and 48 hours, possibly due to instrument variation and manual gatening. However, statistical tests indicated no significant differences aiming the time points. Therefore, samples can be reliably analyzed within 48 hours from the time of collection.