Positron annihilation age-momentum correlation measurements (AMOC) were performed for room temperature ionic liquids (IL) to investigate positronium (Ps) formation process. The solvation time of free electrons in IL is longer than in usual molecular liquids. And hence IL is very useful materials to investigate fast reactions such as Ps formation. On the other hand, Ps formation is a good tool to investigate the dry electrons. The para-Ps annihilation lifetime is about 125ps and then the effect of dry electrons should be seen on the S(t) parameters made by the age-momentum correlation measurements. The slow Ps formation was observed in the room temperature ionic liquids.