The temperature dependence of the molar heat capacity (C_{p, m}^{\circ}) of butylmethacrylate and perdeuterobutylmethacrylate in crystalline, glassy, overcooled liquid, and liquid states has been studied at temperatures between (10 \mathrm{~K}) and (330 \mathrm{~K}) in a vacuum adiabatic calorimetric cryostat within (\pm 0.002 \cdot C_{p, m}^{\circ}). 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_{\mathrm{st}}^{\circ}), the increase in heat capacity on devitrification (\Delta C_{p, \mathrm{~m}}^{\circ}\left(T_{8 \mathrm{~g}}^{\circ}\right)), the zero-temperature entropy (S_{\mathrm{g} i}^{\circ}(0)), the configurational entropy (S_{\text {conf, }}^{\circ}), and the difference in zero-temperature enthalpies of the substances in glassy and crystalline states (\left{H_{88}^{\circ}(0)-H_{\mathrm{cr}}^{\circ}(0)\right}) have been determined. From the values obtained, the thermodynamic functions: (\Delta_{0}^{T} H_{\mathrm{m}}^{\circ}, \Delta_{0}^{T} S_{\mathrm{m}}^{\circ}), and (\Phi_{\mathrm{m}}^{\circ}) have been calculated from (T \rightarrow 0) to (330 \mathrm{~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 \mathrm{~K}) and (p=101.325 \mathrm{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_{\mathrm{m}}^{\circ}) of liquid butylmethacrylate and perdeuterobutylmethacrylate have been estimated. For the same physical states the standard molar entropies of formation (\Delta_{\mathrm{r}} S_{\mathrm{m}}^{\circ}) and the standard molar Gibbs function of formation (\Delta_{\mathrm{f}} G_{\mathrm{m}}^{\circ}) 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.