It has always been a challenge to imitate the lung environment, therefore there is a constant development of standardized in vitro dissolution methods for inhaled products. Dissolution in vitro has been considered as an important parameter, because low solubility determines the bioavailability of inhaled drugs. The in vitro dissolution data generated by the dissolution test experiment can be correlated with in vivo pharmacokinetic data through in vitro-in vivo correlation (IVIVC), because a completed predictive IVIVC model is very useful for drug formulation design and manufacturing changes after approval. The aim of this study was to investigate the effect of the membrane on the dissolution profile of orally inhaled drugs with different solubility, Budesonide (BUD) and Fluticasone propionate (FP) in the different pore sizes of the membrane 8.0 μm, 3.0 μm and 0.4 μm. The method in this study builds on previous dissolution methods, a Transwell® setup to dissolve the drugs with a small amount of dissolution medium, which mimics more the limited lung fluid capacity in vivo. In order to collect the dose from the drugs, Andersen Cascade Impact was used. The dissolution rate of BUD was first in the ranking in all of the pore sizes in the membrane.