Background/Aim. Pathogen inactivation in blood products using riboflavin and ultraviolet (UV) light represents a proactive approach to blood safety, not only for known infectious agents but also for new ones or not yet recognized as threats to the blood supply. This method inactivates a virus, bacteria, fungus, or protozoan pathogen from the blood product without damaging its function or shelf-life. The aim of the study was to study the influence of photoinactivation using riboflavin on the concentration of coagulation factors and coagulation inhibitors in plasma that was treated before freezing. Methods. The examination included 30 units of plasma, separated from whole blood donated by voluntary blood donors around 6 h from the moment of collection. They were treated by riboflavin (35 mL) and UV rays (6.24 J/mL, 265-370 nm) on Mirasol aparature (Caridian BCT Biotechnologies, USA) in approximate duration of 6 min. The samples for examining were taken before (K - control units) and after illumination (I - illuminated units). Results. Comparing the middle values of coagulation factors in the control and illuminated units we noticed their statistically significant decrease in illuminated units (p < 0.001), but the activity of coagulation ones was still in the reference range. The most sensitive coagulation factors to photoinactivation were FVIII, FIX and FXI (21.99%, 20.54% and 17.26% loss, respectively). Anticoagulant factors were better preseved than coagulation factors. Conclusion. Plasma separated from whole blood donation within 6 h, treated with riboflavin and UV light within 6 h from separation and frozen at temperature below -30ºC within 24 h, shows good retention of pro- and anticoagulation activity.