ABSTRACT BACKGROUND: Different hematological analyzers have different analytical performances that are often reflected in the criteria for sample stability of the complete blood count. This study aimed to assess the stability of several hematological parameters using the XN-9000 Sysmex and BC-6800 Mindray analyzers. METHODS: The impact of storage at room temperature and 4 °C was evaluated after 2, 4, 6, 8, 24, 36 and 48 h using ten normal and 40 abnormal blood samples. The variation from the baseline measurement was evaluated by the Steel-Dwass-Critchlow-Fligner test and by Bland-Altman plots, using quality specifications and critical difference as the total allowable variation. RESULTS: Red blood cells and reticulocyte parameters (i.e. hematocrit, mean corpuscular volume, mean corpuscular hemoglobin concentration, red blood cell distribution width, immature reticulocyte fractions, low-fluorescence reticulocytes, middle-fluorescence reticulocytes, high fluorescence mononuclear cells) showed less stability compared to leukocyte and platelet parameters (except for monocyte count and mean platelet volume). The bias for hematocrit, mean corpuscular volume, mean corpuscular hemoglobin concentration and red blood cell distribution width coefficient of variation was higher than the critical difference after 8 h using both analyzers. CONCLUSION: Blood samples measured with both analyzers do not show analytically significant changes in up to 2 h of storage at room temperature and 4 °C. However, the maximum time for analysis can be extended for up to 8 h when the bias is compared to the critical difference.