A recent paper by Homes et al. [Phys. Rev. B 56, 5525 (1997)] reports refle
ctivity spectra of superconducting Nd1.85Ce0.15CuO4 with narrow far-infrare
d lines superimposed to a Drude-like term. We disagree with the assignment
proposed by the authors for those lines and we suggest an alternative inter
pretation. [S0163-1829(98)05146-7].