  In their letter on the quantum Child-Langmuir law, Ang, Kwan and Lau (Phys.
Rev. Lett. 91, 208303 (2003)) include exchange correlation effects within the
Kohn-Sham density functional theory and explore numerically the maximum
transmitted current in nanogaps. We show here that the calculations are in
error as the exchange-correlation component of the chemical potential has been
ignored while fixing the boundary conditions for the Hartree potential.
