Abstract: A process for producing carbo-chain homopolymers, block- and random copolymers of conjugated dienes and vinylaromatic monomers comprising polymerization of dienes, vinyl- or di-vinylaromatic monomers or copolymerization thereof in a medium of a hydrocarbon solvent at a temperature ranging from -30.degree. to +150.degree. C. in the presence of an organolithium catalyst of the formula R(Li).sub.x, wherein R is a hydrocarbon radical or a diene polymer, x is an integer of from 1 to 4, and a modifying additive which is a compound comprising a product of interaction between a phenolamine resin and an alkali metal and having the general formula: ##STR1## wherein n is an integer of from 1 to 10;M is sodium or potassium;R is an alkyl with 2 to 20 carbon atoms or an arylalkyl with 7 to 20 carbon atoms;R.sub.1 is an alkyl with 1 to 6 carbon atoms, an arylalkyl with 7 to 9 carbon atoms or hydrogen;this modifying additive is used in an amount of from 0.07 to 2.0 g/equiv. per one g/equiv. of active lithium.