Until 2003, function of financial markets was price discovery and hedging. From 2003, oil was introduced as an asset and speculators arrived at financial markets to get profit. Entrance of speculators and attenuation of OPEC position due to the lack of the implementation of some past decisions caused different role for OPEC before and after 2003. In this study, for Evaluation of the effectiveness of OPEC news announcements on the crude oil prices, modification of the dummy variables is used. According to the results, adherence pattern of crude oil prices from the lags is different before and after 2003. As well, announcements of increase and maintain production don’t have significant effects after 2003 while the effectiveness of reduction production after 2003 had more continuity in compare of before 2003.