A recently reported off-line procedure to estimate molecular weight (MW) averages and molecular weight distribution (MWD) index, also for polydisperse polymers, directly from their matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra was applied here to poly(bisphenol A-carbonate) (PC), a poly(ether-sulfone) resin (PES), and poly(dimethylphenylene oxide) (PDMPO), all having a wide polydispersity index. The MW and MWD obtained Values were compared with those determined by GPC or supplied by makers. A structural characterization of these polymers was also performed by examining their MALDI-TOF mass spectra.