Outgassing of photoresist materials is a concern for all advanced lithographies. To address this concern, outgassing of photoresist materials exposed at extreme ultraviolet (EUV) wavelengths was studied with a quartz crystal microbalance (QCM) and mass spectrometry and was quantified using the QCM. Mass spectrometry of poly(methylmethacrylate) at 13.4 nm indicated large quantities of hydrogen formed by exposure at EUV wavelengths. QCM studies showed that pure acrylic materials are particularly susceptible to outgassing while pure styrenic materials outgas approximately two orders of magnitude less mass per unit dose. Random copolymers of acrylics and hydroxystyrene, such as found in common 248 nm lithography materials were disproportionately low outgassers. The phenolic moieties randomly introduced into the backbone of acrylics reduced the outgassing by approximately an order of magnitude below what was expected from the pure polymers. It is thought that radical scavenging by phenolic moieties stabilize the acrylic monomers. In addition, judicious selection of the photoacid generator (PAG) is important. It is shown that some PAGs, even at concentrations of 3.8 wt % produce 4 times more volatile mass than the resin itself. The residual solvent left in the film after the postapply bake (PAB) can contribute and even dominate outgassing if the PAB is too low. For the best imaging materials to date, the main sources of outgassing are direct photo/radiolysis of the backbone polymer and the PAG at approximately similar rates, and to a lesser extent, the residual solvent if the PAB is too low. The fate of the outgassed species and their threat to facing optical elements is discussed.