The cationic photopolymerization of tetrahydrofuran  was studied in dichloromethane solution containing  triphenylsulfonium hexafluoroarsenate and one of the following sensitizers Perylene, Phenothiazine or Thioxanthone. The stable cation radicals of the sensitizers are generated by electron transfer. Depending on the sensitizer, two different initiation  pathways  can be identified. This work compares the photopolymerization processes of the three systems.