Photodynamic tumor therapy (PDT) is based upon a photochemical reaction that is limited by the availability of molecular oxygen in the target tissue. The use of hyperbaric oxygenation (HBO) increases the amount of oxygen available for the process may thereby enhance the efficacy of PDT. We proved in a prospective, non-randomized clinical pilot study the acute effects on malignant bronchial stenosis and the technical feasibility of combined PDT/HBO.