A polysiloxane composition includes a polysiloxane, and a first compound. The first compound includes a nitrogen-containing heterocyclic ring structure, and a polar group, an ester group or a combination thereof. A pattern-forming method includes coating the polysiloxane composition on a substrate to be processed to provide a silicon-containing film. A resist composition is coated on the silicon-containing film to provide a resist coating film. The resist coating film is selectively irradiated with a radioactive ray through a photomask to expose the resist coating film. The exposed resist coating film is developed to form a resist pattern. The silicon-containing film and the substrate to be processed are sequentially dry etched using the resist pattern as a mask.