The effect of He/H-2 downstream plasma (DSP) on the mechanical properties of plasma enhanced chemical vapor deposition SiCOH low-k films was studied using nanoindentation (NI) with the continuous-stiffness measurement technique. Furthermore, the main requirements for reliable NI measurements on plasma-modified low-k films are discussed. The results show that the mechanical properties of these films are intimately linked with their porosity and that exposure to He/H-2 DSP causes a change in both the porosity and the mechanical properties of the films. This change is related to the removal of porogen residue formed during the ultraviolet curing of the low-k film.