The polymerization of three analogous monomers-2,2’-thiobisethanol dimethacrylate, 2,2’-oxybisethanol dimethacrylate and 1,5-pentanediol dimethacrylate-has been studied in the temperature range 30-95 degrees C by isothermal d.s.c. The temperature and heteroatom effects on the polymerization course were considered from the point of view of the occurrence and relative importance of hydrogen abstraction reaction which is manifested by chain transfer and chain peroxidation processes. Generally the advantageous effect of the sulfide group is revealed in reduction of oxygen inhibition and suppression of the drop of final conversion with increasing temperature above 70 degrees C in the absence of oxygen. However, the influence of the sulfide group on the polymerization of dimethacrylates is not so great as on diacrylates due to various factors of both a physical and chemical nature.