Two types of methylsilsesquioxanes (MSSQ) were used as base matrix materials for nanoporous films. The hydrophilicity of MSSQ was controlled by copolymerization for the improved miscibility between MSSQs and star-shaped poly(caprolactone) (PCL) as a porogen. Linear relationship holds between porosity/refractive index and vol% of porogen upto 30%. Dielectric constant of porous MSSQ film could be reduced to 2.2 at the porosity of 30 vol%. Dielectric constant was very sensitive to the content of hydroxyl group of MSSQ and the the latter was reduced by treating surface silanols with hexamethyldisilazane.