The pyrolysis and catalytic pyrolysis of polystyrene using a ZSM-5 zeolite catalyst in a fluidised-bed reactor was examined. The effect of zeolite bed loading and particle size on product yields and the composition of the derived oils and waxes were studied. It was found that the pyrolysis and catalytic pyrolysis of polystyrene produced oil, wax and gas products. The gas yield increased with addition of zeolite, and further increased with increasing zeolite bed loading, whilst the wax yield decreased. The oil yield remained above 90% of the feed. Reducing the zeolite particle size was found to have a similar effect on the product yield as increasing the zeolite bed loading. The gas composition consisted of hydrocarbon gases ranging from C-1 to C-4 and ethene and propene gases were found to be the most abundant. The oils and waxes were analysed and the aromatic hydrocarbons characterised and quantified. Uncatalysed oils were found to contain large amounts of styrene, with small amounts of single-ring aromatic compounds and polycyclic aromatic hydrocarbons. However, increasing the zeolite bed loading decreased the styrene concentration and increased the concentration of non-styrene single-ring hydrocarbons and also two- and three-ring aromatic compounds.