  In a recent Letter Morita, Kohmoto and Maki analyzed the structure of
quasiparticle states near a single vortex in a d-wave superconductor using an
approximate version of the Bogoliubov - de Gennes theory. Their principal
result is the existence of a bound state within the core region at finite
energy with full rotational symmetry, which they assert explains the recent
scanning tunneling microscopy results on YBCO single crystals. Here we argue
that the approximation used in this work is fundamentally inadequate for the
description of a d-wave vortex and that the obtained circular symmetry of the
local density of states is an unphysical artifact of this approximation.
