Porous poly(vinylidene fluoride) (PVDF) membranes for dehumidification were prepared from a PVDF/dimethylformamide/water system by phase inversion with poly(ethylene glycol) (PEG) as an additive at various concentrations (1.2, 1.8, and 2.4%) and with various molecular weights (1000, 2000, and 6000). The surface morphologies of the resultant membranes were characterized with scanning electron microscopy and atomic force microscopy, and the pore diameter, porosity, and pore size distribution of the membranes were also determined by a gas-sorption method. The influence of the concentration and molecular weight of PEG on water-vapor transport through the membranes was evaluated. The moisture-transport property of the membranes was improved significantly with increases in the concentration and molecular weight of PEG, and a membrane with good moisture permeability was obtained with 2.4% PEG-6000 as an additive. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 2696-2703, 2010