The causes of hallucinations in lung cancer are as follows: a. lung cancer causes lung dysfunction, which leads to respiratory failure and pulmonary encephalopathy, resulting in patients’ hallucinations; b. brain metastasis of lung cancer causes brain dysfunction, which leads to patients’ hallucinations; c. ion disorders in lung cancer patients, such as low sodium and low chloride, hypercalcemia, etc., which cause patients’ hallucinations. When lung cancer patients have hallucinations, it is important to clarify the cause. If the patient is caused by pulmonary encephalopathy, it is recommended to treat respiratory failure; if the patient is caused by brain metastasis and cerebral edema, it is recommended to gradually lower cranial pressure and treat brain metastasis; if it is caused by ionic disorder, it is recommended to correct ionic disorder treatment.