X-Ray photoelectron spectroscopy is used to elucidate the chemical environments of the atoms in as-deposited plasma-polymerized acrylonitrile (PPAN) thin film and PPAN films pyrolysed at the temperatures 573 and 773 K. The photoelectron spectra are collected at the electron take-off angles of 20-degrees and 70-degrees. The C 1s, N 1s, and O 1s spectra of all the samples demonstrate clearly that the structural modifications take place owing to pyrolysis in the PPAN structure. Apart from the structural modifications, a decrease of nitrogen and an uptake of oxygen are evidenced. A few chemical species other than the usual ones are also detected.