The article deals with the relations between the Comintern, Soviet Russia and Mexico (with its Left-Wing movement, first of all). Both Soviet Russia and Mexico almost simultaneously had had revolutions which changed enormously all the shape of these countries. The radical (although not Socialist one) character of Mexican Revolution influenced a lot the possibilities of the Comintern's activities in Mexico. The author analyzed the successes and failures of Moscow in Mexican Left-Wing and workers' movement in 1919-1921, stressing its objective and subjective causes.