The inhalation route is of increasing interest for both local and systemic drug delivery, including macromolecular biopharmaceuticals, such as peptides, proteins, and gene therapeutics. In addition to appropriate aerosolization for deposition in relevant areas of the respiratory tract, therapeutic molecules may require an advanced carrier system for safe and efficient delivery to their target. Two approaches to obtain novel carrier systems for pulmonary drug delivery are large porous microparticles with a low aerodynamic diameter and lectin-functionalized liposomes. Epithelial cells of alveolar or bronchial origin, obtained either from patient material or from established cell lines, can be grown on permeable filter supports, resulting in polarized monolayers with functional intercellular junctions. With such in vitro models, transport of drugs into pulmonary epithelial cells and/or across the air-blood barrier, as well as the effect and efficacy of novel drug carrier systems can be systematically studied.