In this project several topics for virtual endoscopy in the context of nasal sinus surgery were worked on. For difficult cases in endoscopic sinus surgery, a careful planning of the intervention is necessary. Due to the reduced field of view during the intervention, the surgeons have less information about the surrounding structures in the working area compared to open surgery. Virtual endoscopy enables the visualization of the operating field and additional information, such as risk structures (e.g., optical nerve and skull base) and target structures to be removed (e.g., mucosal swelling). During the design of a system for pre-operative planing and patient education, input devices as well as rendering techniques were developed. The last iteration of the project resulted in a stand-alone CT data viewer optimized for depicting the nasal sinuses. Through the use of GPU-ray-casting and customized shading, an interactive explorer was developed. This system was successfully deployed to the clinical partners (ENT – department of the University Clinic Leipzig, and Kopfzentrum Leipzig) for evaluation.