Objectives: To examine and compare the clinical manifestations of lung cancer between the age groups of 40 years or less and over 40 years at Maharaj Nakorn Chiang Mai Hospital from January 2002 - December 2003.
Material and Method: Six hundred and nineteen patients with confirmed pathological cell type lung cancer were newly registered.
Results: The mean age was 60.1 years and male to female ratio 1.79:1. Their smoking history was presented in 72% of patients, with cough being the most common symptom followed by weight loss, dyspnea, chest pain, and hemoptysis with a median duration of 2 months. Mass or nodule was the most common radiographic finding, and adenocarcinoma was the most common pathological cell type. Most of the patients (82.4%) presented in the advanced stage. There were 19 patients (3.1%) aged equal to 40 years or less. In this group, chest pain and adenocarcinoma were presented more significantly, while a smoking history was found to be less significant in females. The duration of symptoms in this group tended to be shorter (1.3 months), but not statistically significant. More than 80% of both patient groups presented in the advanced stage.
Conclusion: Lung cancer in the young is uncommon, but most clinical manifestations are not different from older patients. The less significant smoking history, especially in females, tendency of shorter duration of symptoms, and more frequent adenocarcinoma in the younger patients may have some factors that are associated and should be studied further.

Keywords: Lung cancer, Clinical manifestation, Young age