In scope of this paper, dielectric and electro-optic properties of planar aligned ferroelectric liquid crystals/carbon nanotubes dispersions were investigated. It is demonstrated that even a small concentration of nanotubes greatly affects the performance of the liquid crystal cells. The obtained experimental results are explained by the trapping of ions through the carbon nanotubes, which results in a significant modification of the internal electric field as well as the space charges distribution inside the liquid crystal cells.