One fourth of all people with lung cancer have no symptoms when the cancer is diagnosed. These cancers are usually identified incidentally when a chest x-ray is performed for another reason. The other three fourths of people develop some symptoms. The symptoms are due to direct effects of the primary tumor; to effects of metastatic tumors in other parts of the body; or to malignant disturbances of hormones, blood, or other systems.
Symptoms of primary lung cancers include cough, coughing up blood, chest pain, and shortness of breath.

A new cough in a smoker or a former smoker should raise concern for lung cancer.
A cough that does not go away or gets worse over time should be evaluated by a health care provider.
Coughing up blood (hemoptysis) occurs in a significant number of people who have lung cancer. Any amount of coughed-up blood should cause alarm.
Chest pain is a symptom in about one fourth of people with lung cancer. The pain is dull, aching, and persistent and may involve other structures surrounding the lung.
Shortness of breath usually results from a blockage in part of the lung, collection of fluid around the lung (pleural effusion), or the spread of tumor through the lungs.
Wheezing or hoarseness may signal blockage or inflammation in the lungs that may go along with cancer.
Repeated respiratory infections, such as bronchitis or pneumonia, can be a sign of lung cancer.

Symptoms of metastatic lung tumors depend on the location and size. About 30-40% of people with lung cancer have some symptoms or signs of metastatic disease.

Lung cancer most often spreads to the liver, the adrenal glands, the bones, and the brain.
Metastatic lung cancer in the liver usually does not cause any symptoms, at least at the time of diagnosis.
Metastatic lung cancer in the adrenal glands also typically causes no symptoms at the time of diagnosis.
Metastasis to the bones is most common with small cell type cancers but also occurs with other lung cancer types. Lung cancer that has metastasized to the bone causes bone pain, usually in the backbone (vertebrae), the thighbones, and the ribs.
Lung cancer that spreads to the brain can cause difficulties with vision, weakness on one side of the body, and/or seizures.

Paraneoplastic syndromes are the remote, indirect effects of cancer not related to direct invasion. Symptoms include the following:

Clubbing of fingers - The depositing of extra tissue under the nails
New bone formation - Along the lower legs or arms
Anemia - Low numbers of red blood cells and high calcium level or low sodium level in the blood
Other effects - Muscle weakness, skin rashes, and degeneration of the brain
Weight loss
Fatigue
Low sodium levels