The interaction between charged colloidal particles confined between two parallel charged plates is investigated theoretically. We propose a simple model with a space-dependent Yukawa pair potential between the colloids which is derived from lineal screening and density functional perturbation theory. Within this model, the density profile of the confined colloidal particles is obtained by computer simulation. In the absence of van der Waals attractions between the walls and the colloidal particles, there is no practical difference in the colloidal density profiles as compared with those obtained with the usual space-independent Yukawa pair potential. However, there can be large deviations if an additional large wall attraction is present.