In this work, we investigated the optical properties of diffraction gratings fabricated using in-plane switching cells and polymer-dispersed liquid crystal (LC) materials. The diffraction intensities of the zeroth and first diffraction orders strongly depend on the applied voltage as well as the polarization of light. In particular, a study of the intensity of the first diffraction order for the p-polarized light as a function of the applied voltage shows a bell-shaped peak; the peak voltage can be controlled by varying the preparation process and LC concentrations. Our results demonstrate that these cells are promising for developing switchable diffraction gratings.