The temperature dcpendence of the molar heat capacity C(p,m)-degrees of butylmethacrylate and perdeuterobutylmethacrylate in crystalline, glassy, overcooled liquid, and liquid states has been studied at temperatures between 10 K and 330 K in a vacuum adiabatic calorimetric cryostat within +/- 0.002 . C(p,m)-degrees. The temperature and enthalpy of melting of the compounds have been measured. The quantities of the glass transition and the glassy state such as the glass-transition temperature T(gt)-degrees, the increase in heat capacity on devitrification DELTAC(p,m)-degrees(T(gt)-degrees)), the zero-temperature entropy S(gt)-degrees(0), the configurational entropy S(conf)-degrees, and the difference in zero-temperature enthalpies of the substances in glassy and crystalline states {H(gt)-degrees(0) - H(cr)-degrees(0)} have been determined. From the values obtained, the thermodynamic functions : DELTA0(T)H(m)-degrees, DELTA0(T)S(m)-degrees and PHI(m)-degrees have been calculated from T --> 0 to 330 K. From the enthalpies of formation of polybutylmethacrylate and polyperdeuterobutylmethacrylate obtained from enthalpies of combustion of the polymers in highly elastic states at T = 298.15 K and p = 101.325 kPa as well as the enthalpies of polymerization of the monomers in bulk measured by direct calorimetry, the standard enthalpies of formation DELTA(f)H(m)-degrees of liquid butylmethacrylate and perdeuterobutylmethacrylate have been estimated. For the same physical states the standard molar entropies of formation DELTA(f)S(m)-degrees and the standard molar Gibbs function of formation DELTA(f)G(m)-degrees for the compounds have been calculated. The quantitative influence of the substitution of hydrogen for deuterium on the thermodynamic properties of butylmethacrylate has been revealed.