A very large surface to volume ratio of nanoporous silicon (PS) produces a high density of surface states, which are responsible for uncontrolled oxidation of the PS surface. Hence it disturbs the stability of the material and also creates difficulties in the formation of a reliable electrical contact. To passivate the surface states of the nanoporous silicon, hydrocarbon films prepared by plasma enhanced chemical vapor deposition of methane (PECVD) have been deposited on porous silicon (PS). Conduction properties as well as optical characteristics of the as-deposited samples and annealed ones have been studied by current-voltage (I-V) and capacitance-voltage (C-V) measurements, spectral response, ellipsometry and Fourier transform infrared spectroscopy (FTIR) as a function of the annealing temperature, ranging from 200 to 750 °C. By high-temperature treatment, the low rectifying I-V curves become strong rectifying and C-V curves are similar to those of metal-insulator-semiconductor structures. These characteristics were explored and can be appropriately used in the fabrication of optoelectronics and sensor devices based on PS.