BackgroundExtracorporeal photopheresis (ECP) treatment, mostly based on apheresis technology, is used for immunomodulation in various diseases such as cutaneous T‐cell lymphoma, graft versus host disease and other (auto)immune disorders. The aim of this study was to collect high cell counts and purity in shorter procedure times using an ECP off‐line system with an increased collection flow rate of 2 mL/min to a target volume of 200 mL buffy coat.Study design and methodsIn this prospective study, data of routinely performed off‐line photopheresis treatments were collected and analyzed at the Central Institute for Blood Transfusion & Department of Immunology (ZIB) of the Tirol Kliniken, to assess absolute cell counts and procedure times and to calculate collection efficiencies (CE2).ResultsA total of 22 patients participated in this study. The processed blood volume was 4312 mL, the collection time 120 min, overall procedure time 157 min and the absolute cell counts of treated white blood cells (WBC) and mononuclear cells (MNC) were 5.0 and 4.3 × 109 respectively (median values). The calculated CE2 for WBC and MNC was 21.1% and 58.5%, the proportion of treated MNCs of the total number of MNCs present was 55.0%.ConclusionThe data presented in this study show high therapeutically effective cell counts collected with a high MNC purity within a shorter overall collection/procedure time due to an increased collection flow rate.