Nanoindentation was used to determine reduced elastic modulus Er and hardness H of 16 mu m thick Parylene C coatings vapor-deposited on mill-finished samples of aluminum, copper, nickel steel, and stainless steel. Profilometry was used to compare average surface roughnesses of the polymeric coatings to the roughnesses of the underlying metals, thereby providing a quantitative index for determining conformality. Roughness, elasticity, and hardness of coatings were found to be affected by both chemical composition and surface roughness of four different metallic substrates. Standard nanoindentation evaluations of Er and H distributions for the various metals were found to be positively skewed, which precluded use of simple averages for purposes of comparison. However, analysis of the nanoindentation and profilometry data by use of alternative techniques indicated that coatings were consistently smoother and flatter than their underlying substrates, i.e., they were not truly conformal, and nanomechanical properties of Parylene C were affected by the chemical composition of the substrates independently of the effects of substrate roughness. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 127: 2969-2976, 2013