Cationic copolymerization of tetrahydrofuran (THF) with ethylene oxide (EO) in the presence of diols leads to dihydroxy terminated telechelic copolymers. In the present article the influence of copolymerization conditions on the copolymer structure was studied in view of conclusions derived from studies of copolymerization kinetics and mechanism, It was shown that according to established copolymerization mechanism. the number average molecular weights increase linearly with conversion up to M-n congruent to 2500, hydroxyl rod groups are bound exclusively to EO units and copolymers are composed of [EO]-[THF], segments. Microstructure of copolymer may be to some extent regulated by changing reaction conditions. Some physical properties of copolymers also were studied.