Here we have proposed a modified Cassie-Baxter model to investigate the influence of particle size on superhydrophobic behavior of silica nanosphere arrays. An assembly technique enabled to prepare wellordered silica nanosphere arrays, and then the silica arrays were fluorinated by a spin-coating process. Compared with a F-coated flat surface, the contact angle on fluorinated silica nanoarrays reached a value of 152 +/- 1.4 degrees. A Cassie-Baxter parameter, surface fraction ((phi(S)), was used to simulate the hydrophobicity. It was found that the nanosphere size played an important role in affecting the hydrophobicity of the sphere arrays. The present work demonstrates that the superhydrophobicity ofnanoarrays is well correlated with the modified Cassie-Baxter model. (c) Koninklijke Brill NV, Leiden, 2008