Thermal behaviour of poly(vinyl chloride-co-vinyl acetate) and its laser-derived, partly crosslinked analogue having less pendant groups and some conjugated C=C bonds was examined by means of TGA technique and compared. The major degradation differences relate to the decomposition progress, evolution of volatile products and the yield of a carbonaceous residuum. The more feasible cleavage of acetate-and Cl-pendant groups and the higher yield of carbonaceous residuum observed with the laser-derived analogue are respectively explained by the accelerating effect of the conjugated C=C double bonds and crosslinking. (C) 2006 Elsevier B.V. All rights reserved.