A porous organosilica glass (OSG) film consists of a single phase of a material represented by the formula Si.sub.vO.sub.wC.sub.xH.sub.yF.sub.z, where v+w+x+y+z=100%, v is from 10 to 35 atomic %, w is from 10 to 65 atomic %, x is from 5 to 30 atomic %, y is from 10 to 50 atomic % and z is from 0 to 15 atomic %, wherein the film has pores and a dielectric constant less than 2.6. The film is provided by a chemical vapor deposition method in which a preliminary film is deposited from organosilane and/or organosiloxane precursors and pore-forming agents (porogens), which can be independent of, or bonded to, the precursors. The porogens are subsequently removed to provide the porous film. Compositions, such as kits, for forming the films include porogens and precursors. Porogenated precursors are also useful for providing the film.