A seeding method was used to synthesise zeolite Y and zeolite ZSM-5 films on porous a-alumina supports with an average pore size of 100 nm in the top layer. The feasibility of zeolite Y film synthesis was investigated by changing different synthesis parameter. These parameters were synthesis time, position in the synthesis solution, rinsing and drying. The surface charge of the supports were modified with a polymer solution prior to the seeding with zeolite Y crystals and than placed in the synthesis solution to grow the film. It was found by SEM analyses that the film thickness was between 0.5 mm and 1.5 mm and increased with the synthesis time. Permeation measurements with helium, nitrogen and sulphurhexafluoride show very high permeances and low selectivities. The reason for this is defects such as cracks that were found with SEM analyses. Under the investigated conditions it was not possible to achieve a dense continuous film without defects. Zeolite ZSM-5 films were synthesised with 3 different synthesis times - 6h, 10h and 18h. The treatment of the support was similar to that for the zeolite Y synthesis. Silicalite-1 crystals were used as seed crystals. It was found that with 6h and 10h synthesis time no continuous films could be obtained. Compared to earlier studies, permeation measurements showed higher permeances and lower selectivities. This might be due to small defects in the film that could not be found with the SEM.