The capatiance–voltage characteristics associated with the hole accumulation in hydrogenated amorphous silicon metal–insulator–semiconductor structures were investigated. The capacitance was measured by using an ac voltage and a quasistatic method. In the ac measurements, we observed the partial response of the hole capacitance, while the full response of the hole capacitance was confirmed by quasi-static measurements. The effect of illumination on the hole capacitance was also investigated. One possible mechanism accounting for the frequency and temperature dependencies of the hole capacitance is proposed.