The patients with nasal valve incompetence usually have a narrow nose. When breathing deeply through the nose, a tendency to collapse is observed in the nasal side walls. Cottle maneuver is important in evaluation of the patients. In that maneuver, when the patient exhales normally, the cheek of the side of the nostril examined is pulled out (laterally and upward). If breathing is relieved, the test is positive. Also, other causes of nasal obstruction except nasal valve should be investigated.The investigation may be performed with speculum for nasal septum, and with an endoscope for posterior part of the septum, concha, opening of the sinüs channels in the nose.

The endoscope for nasal examination is a 2.7 or 4 mm thick device with a tiny camera and light at the tip. The examinations are painless and short. In diagnosis of nasal valve incompetence any further investigation is not required but acoustic rhinometry and rhinomanometry tests can provide objective evidence of a nasal valve constriction. If the nasal valve incompetence is accompanied by septum deviation, concha hypertrophy, sinusitis and other problems such as polips, sinus tomography is helpful to evaluate the nose and surrounding structures.