This study investigates whether the information regarding the safety of genetically modified (GM) corn and GM corn oil can significantly affect the Japanese consumers' risk perceptions and whether these risk perceptions can determine their willingness-to-pay (WTP) premium for non-GM corn oil.  This WTP premium was measured by using a contingent valuation method that is commonly applied for valuing non-market commodities.  Our empirical results show that, when the scientific knowledge of the safety of GM corn and GM corn oil was provided, the risk perceptions expressed by the mean of a probability distribution and those by the variance both substantially decreased, while the WTP unchanged with the given information.  In addition, Japanese consumers' premium percentage for non-GM corn oil was found to be about 40% of the price of the cooking corn oil sold in markets.