  In a recent study [Phys. Rev. E 60, 6530 (1999)], Trizac and Raimbault showed
that the effective pair interaction between like charged colloids immersed in a
cylindrically confined electrolyte remains repulsive even when the size of the
micro-ions or the finite longitudinal extension of the confining cylinder are
taken into account. Contrary to their claim, we argue that the case of finite
longitudinal confinement doesn't always generate repulsive interactions and to
illustrate this point we also provide a simple example.
