Structures in the angular distribution of helium atoms inelastically scattered by the graphite (0001) surface were recently explained as inelastic selective adsorption processes. The resonant transition in a bound state of the gas-surface potential, reached after the exchange of one phonon, can occur also without the exchange of a reciprocal lattice vector. This “specular” inelastic selective adsorption is observed as large maxima in the inelastically scattered intensity. Detailed measurements of this process are reported here for the first time. They are taken both at different incident angles and at different surface temperatures T S. The experimental observations are compared with one-phonon inelastic calculations. Good agreement is found at low T S, while the disagreement obtained at higher temperatures seems to indicate the failure of the one-phonon approximation already at T S ≳ 100 K. Specular inelastic selective adsorption associated with out-of-plane phonons is suggested to be a possible reason for the sizeable drop of elastic intensity often observed near grazing incidence.