Aim . To study microrheological properties of RBCs and capillary blood flow parameters using optical methods in patients with arterial hypertension (AH) and type 2 diabetes mellitus (DM2). Methods . RBCs aggregation properties were evaluated in vitro using laser aggregometry and optical trapping. Сapillary nail refill was evaluated in vivo using nailfold digital capillaroscopy. Results. The aggregation of RBCs in patients suffering from AH was higher compared to healthy subjects who demonstrated a decrease in the aggregation time by 29±9%. A similar trend was observed in patients with AH and DM2. The comparison of the results obtained by different methods showed that patients with AH with a high capillary blood flow velocity measured in vivo reported a decrease in the aggregation index by 14±4% compared to patients with low velocity. Conclusion. The comparison of microrheological blood properties in patients with AH and AH+DM2 versus the control group showed statistically significant differences in the aggregation index that was higher in AH patients. These differences were more pronounced in patients with AH and DM2. The results obtained by in vitro and in vivo methods were consistent.