There are many reasons for unilateral poor nasal ventilation, the most common being nasal septal deviation or turbinate hypertrophy. The bony crest of the deviated septum may block nasal ventilation on the side of the deviation, which occurs alternately, especially in the lateral position when the nostril is better ventilated toward the upper nostril and worse ventilated toward the lower nostril. Thick hypertrophied inferior turbinates may also cause poor nasal ventilation, which can be treated by correction of nasal septum deviation or partial excision of turbinates. In addition, there are benign and malignant masses in the unilateral nasal cavity. Benign masses are more common, such as papilloma or nasal hemangioma on one side. Malignant masses are relatively rare, such as squamous cell carcinoma of the maxillary sinus. Nasal endoscopy or sinus CT can be done first. If there is bone destruction, malignancy is considered more likely, however, papilloma may also cause bone destruction. Pathological examination can be done if necessary, and if a swelling is indeed found in the nasal cavity, most of them consider surgery. In addition, there are swellings in the nasopharynx, such as residual glands, and sometimes pathological examinations of the nasopharynx are taken to further diagnose the benignity and malignancy of the swelling.