AbstractPlatelet concentrates (PC) were stored for 6 days in either polyolefin (PO) or polyvinylchloride/di‐(2‐ethylhexyl)phtalate (PVC/DEHP) bags in 100% plasma or in a synthetic medium with 35 or 10% plasma. For all conditions studied the usual in vitro parameters were well maintained, with a pH above 6.8. In both bag types platelets can be satisfactorily stored for 6 days in a synthetic medium with minimal amounts of residual plasma. For this medium, the PO bag offers a slight advantage with respect to the preservation of platelet ATP content (>80 versus>70% in the PVC bags) and aggregation and adhesion capacity. The adhesion capacity increased in the PO bags, while it decreased in the PVC b