Background: Prolonged storage of platelets could improve availability and logistical management and decrease wastage. Immunobiochemical methods can be used to guarantee the quality of platelets after prolonged storage. Objective: The aim of this study was to compare storage-related changes in buffy coat-derived platelet concentrations versus platelet-rich plasmal. Methods: Units of whole blood were drawn using a quadruple-bag blood container system. Platelet-rich plasma and buffy coat prepared from whole blood following standard methods were stored for 9 days. During this period test samples were aseptically collected for analysis on Days 1, 2, 3, 5, 7 and 9. Results: The highest CD42b expression was greater than 95%. The percentage of CD62p was significantly lower than the CD42b expression. The pH remained fairly stable during storage. Measurement of pO2 and pCO2 showed that oxygen levels were significantly higher than carbon dioxide levels. There were no significant differences in bicarbonate levels, glucose consumption and lactate production between the groups. The swirling effect with platelet-rich plasma samples decreased after 5 days of storage and after 7 days of storage for buffy coat samples. There was a significant twenty-fold increase in the mean IL-1β after 5 days of storage for both groups. Slight increases in IL-6 and IL-8 levels were seen at 5 days. Conclusion: The quality of platelet concentrates remained acceptable during 7 days of storage in respect to the swirling effect, pH and platelet activation. There were no significant differences between buffy coat-derived platelets and platelet-rich plasma in this study.