During the last decade, minimized extracorporeal circulation (MECC) systems have shown beneficial effects to the patients over the conventional cardiopulmonary bypass (CECC) circuits. This is a prospective randomized study of 99 patients who underwent coronary artery bypass grafting (CABG) surgery, evaluating the postoperative haematological effects of these systems. Less haemodilution (p=0.001) and markedly less haemolysis (p<0.001), as well as better preservation of the coagulation system integrity (p=0.01), favouring the MECC group, was found. As a clinical result, less bank blood requirements were noted and a quicker recovery, as far as mechanical ventilation support and ICU stay are concerned, was evident with the use of MECC systems. As a conclusion, minimized extracorporeal circulation systems may attenuate the adverse effects of conventional circuits on the haematological profile of patients undergoing CABG surgery.