The functionalization of poly(styryl)lithium with styrene oxide as a route to functional polymers was investigated. When the reaction was performed in benzene at room temperature, analysis of the products by SEC and column chromatography indicated the presence of functional polymer (83.5 wt %), along with unfunctionalized polymer (9.0 wt %), dimeric product (5.6 wt %), and trimeric product (0.1 wt %). The structure of the dimeric product was determined to be head-to-head dimer from both 13C NMR analysis and MALDI−TOF MS and was proposed to result from an electron-transfer mechanism. The dimeric product was eliminated when the functionalization was effected in the presence of tetrahydrofuran (>15 mol equiv). Under these conditions >99 wt % functionalized polymer was obtained as determined by column chromatography and MALDI−TOF MS. Addition of PSLi to the epoxide can occur by addition to the least hindered carbon or by addition to the most hindered carbon. Analysis of the regiochemistry of the chain end was performed by both 13C NMR and APT 13C NMR spectroscopy. It was determined that the product obtained in the presence of tetrahydrofuran contained 53 mol % of the product resulting from addition to the least hindered carbon and 47 mol % resulting from addition to the most hindered carbon.