The diagnosis of nasal polyps is usually done by looking inside your nose with an endoscope. This is a special lighted camera that can see further into your nose, where the sinus cavities drain. Some nasal polyps are so large that they can be seen just looking naturally into the nose. Once they are seen, further tests are usually done, including a CAT scan of your sinuses. This will tell us the extent of the polyps and which sinus cavities are involved.