Two commercially available packaging-derived fuels (PDFs), obtained as a result of recycling programs for municipal solid wastes, were fed batchwise into two laboratory scale bubbling fluidized bed combustors. One fuel tested came from a mono-material collection of PET bottles while the other was obtained by means of a mechanical selection of plastic containers. Two experimental procedures were set up to separately investigate primary fragmentation of fuels and carbon fines generation from devolatilized particles. Results were compared with those obtained with three other waste-derived fuels, namely a refuse-derived fuel, a tyre-derived fuel and an ebonite. After devolatilization, PDF particles generated char-sand aggregates that greatly increased the fixed carbon residence time in the fluidized bed reactors. Carbon fines generation rates, under both inert and oxidizing conditions, were much lower than those measured in the tests with other high-volatile fuels. A new descriptive model was proposed to describe the overall combustion-comminution pattern of fixed carbon during the fluidized bed combustion of the packaging-derived fuels tested.