The pervaporation performance of polydimethylsiloxane (SR) spin- and dip-coated polyetherimide (PEI) membranes was investigated for acetic acid/water mixture. The spin-coating technique was used to produce a thin, uniform coating, and compared to the dip-coating technique in terms of pervaporation performance, thickness, and uniformity of the coating layer. It was found that the PEI membranes studied were water-selective and that the water selectivity of PEI membranes increased when spin-coated with a SR solution. It was also found that the water selectivity increased when the PEI membranes were coated with SR solutions of increasing concentration, although the permeate flux noticeably decreased. The coating thickness was measured by the weighing technique and the results were compared with the thickness estimation by two versions of the resistance model. It was determined that the spin-coating technique can provide a thinner and more uniform coating than the dip-coating technique, and that the coating solution penetrates the membrane pores before coating the surface.