In recent years, the international oil price has fluctuated violently, bringing about huge risk for the international oil trade. In fact, the risk of crude oil and petroleum product imports is different because of the different import origins and prices. Which import risk is lower for China? From the perspective of oil supply security, how should China portfolio crude oil and petroleum product imports to minimize its oil import risk? Using portfolio theory and a diversification index approach, this paper compares and analyzes the supply, price and transport risks of crude oil and petroleum product imports. Our results show that the following: (1) Specific risk (diversification risk) and marine transport risk of China's petroleum product imports are lower than that of crude oil imports. (2) The average rate of return of China's petroleum product imports is higher than that of crude oil imports. Moreover, the average import price variance of petroleum product imports is lower than that of crude oil imports. Thus, the systematic risk (price risk) of petroleum products is lower too. Therefore, from the perspective of oil supply security, China should increase petroleum product imports to decrease its oil import risk. (C) 2009 Elsevier Ltd. All rights reserved.