Abstract A detailed study of the dependence of the optical constants of homogenous chemical vapor deposited hydrogenated amorphous silicon on the preparation conditions is reported in this work. It is established that the optical band gap, E g refractive index, n, at a wavelength of 2000 nm, coefficient B derived from the Tauc plot, and the inhomogeneity, Δd, depend on the pressure of the gases during deposition. The optical gap, growth rate, and inhomogeneity increase with increasing gas pressure. These parameters also depend on the substrate temperature and growth rate. These results are discussed in terms of the gas-phase reactions.