Contemporary separation technology of great interest is high quality membranes, possessing high flux and selectivity together with high durability. Supported membranes based on thin MFI zeolite films and graded supports response to the mentioned requirements to a higher extent. To maintain separation efficiency in a high level, powerful fabrication and characterization techniques of membranes are essential. For the last decade, several techniques for characterization of defects have emerged. Of special interest is adsorption-branch permporometry based on measuring the flow of noncondensable gas, e.g. helium, through membrane as a function of the activity of condensable vapour, normally n-hexane or p-xylene. In the present work, silicalite-1 membranes with a thickness of 500 nm were prepared by using seeding method. After the preparation, membranes were characterized by single gas permeation and n-hexane/helium permporometry and then, tested for separation of a mixture of hexane isomers: n-hexane and 2,2-dimethylbutane (DMB). The results of the work showed that single gas permeation data cannot be used for membrane quality estimation. No correlation between single gas permeation data and n-hexane/helium permporometry data has been discovered as well as between single gas permeation data and separation data. The separation experiments showed that the dependence of the separation factor on temperature is quite spontaneous and unpredictable. On the other hand, it was shown that the DMB permeance at room temperature in a n- hexane/DMB mixture can be predicted by permporometry data. Also, an empirical correlation between n-hexane permporometry and the separation data has been found. Finally, the present work also demonstrated the strength of adsorption branch permporometry for zeolite membrane quality characterization.