Objective: Photodynamic therapy is an effective cancer treatment, but light delivery constraints currently limit its application to superficial, easily visualized tumors. The goal of this study was to determine whether it would be possible to manipulate the optical properties of irregularly shaped anatomic structures for the purpose of light delivery. Such a technique could potentially expand the role of photodynamic therapy to treat tumors currently viewed as inaccessible to visible light. Methods: Ex vivo sheep tracheas and lungs were filled with substances of varying refractive indices. The effects on transmission of visible light of a known wavelength introduced into the proximal lumen of the organs were studied. Data were collected with naked-eye observation, standard photography, charge-coupled device imaging, and direct light measurement. Results: Filling a lung or trachea with a liquid possessing a refractive index higher than that of tissue dramatically increases the ability to deliver light around bends and through a branched network. Conclusion: It is possible to manipulate the optical properties of an ex vivo organ for the purpose of enhanced light delivery.