The hair treatment composition, which is in the form a pearlescent product, contains a nonionic, amphiphilic associative thickener consisting of at least one hydrophobically modified aminoplast/polyether copolymer; a hair care active ingredient selected from the group consisting of cationic surfactants, zwitterionic surfactants, cationic polymers, cationic silicone compounds, amine-substituted silicone compounds, cationic derivatized proteins, cationic derivatized protein hydrolyzates and betaines; and a pearlescence or turbidity-inducing agent selected from the group consisting of fatty acid alkanol amides, fatty acid glyceryl esters, guanine, glycol fatty acid diesters, styrene/acrylate copolymers, polyethylene glycol fatty acid diesters, styrene/vinyl pyrrolidone copolymers and poly(trimethylammonium ethylmethacrylate chloride); in an aqueous cosmetic base. The composition is usable as a leave-in hair care composition or a hair rinse, which conditions the hair and imparts luster and volume to the hair.