This paper refers to the influence of the catalysts boron trifluoride p‐methoxyaniline complex (BF3 · MA) and boron trifluoride etherate complex (BF3 · Et2O) having different reactivity in cationic copolymerization of phenyl glycidyl ether (PGE) with γ‐butyrolactone (γ‐BL) and ϵ‐caprolactone (ϵ‐CL), respectively. Reactions were followed by FT‐IR, HPLC and SEC. SEC with multiple detection and Two‐Dimensional‐Chromatography HPLC/SEC were used to characterize the products in view to their copolymer compositions. In the presence of BF3 · MA a preferred formation of spiroorthoesters (SOE) was observed; the polymerization of SOE under these conditions can be neglected. In case of the more reactive BF3 · Et2O the epoxide homopolymerization strongly competes with SOE formation, resulting in a product mixture of epoxide homopolymers (and in the case of ϵ‐CL also lactone homopolymers) and copolymers with low lactone content.