The effect of a thin, dielectric buffer layer on coplanar electrode structures is examined. The buffer layer is placed between the metal electrodes and the dielectric substrate. It is seen to have a significant effect on the charge distribution, field distribution, and capacitance. A new approximate formula is derived for the charge in the presence of the buffer layer, which allows the fields to be calculated efficiently. In addition, closed form approximate expressions are derived for the capacitance. The expression for the charge is based on the observation that it's distribution in the presence of a buffer layer is almost the same as that for a microstrip The formulas are compared to results from a moment method solution for the problem