The standard way for fighting rural poverty and improving food production efficiency is to move toward free trade. However as underlined by several economists, markets imperfections may hamper the positive impact of trade liberalization. In this paper, the consequences of imperfect information on agricultural markets are evaluated through the results of two versions of a world dynamic CGE model: one is based on standard markets equilibrium assumption for each product and factor, while the other includes imperfect information on agricultural commodities markets. Impacts on GDP performances and on household welfares for selected countries are presented. It appears that in the case of imperfect information most of the gains related to comparative advantages vanish, due to highly fluctuating agricultural prices. Then it is impossible for economic actors to predict prices accurately enough to take efficient decisions and policies able to reduce this imperfection may improve the global welfare.