Objectives: To assess the diagnostic value of bronchoalveolar lavage fluid (BALF) ferritin as a lung tumor marker by comparing serum and BALF ferritin concentrations in patients with peripheral lung cancer versus control subjects with benign lung disease, and to examine the theory of ferritin compartmentalization around the tumor area by comparing ferritin concentrations in serum and bilateral (affected and unaffected side) BALF in cancer patients. Methods: Four groups of patients were investigated: 10 control nonsmokers, 10 control smokers, 10 smokers with chronic obstructive pulmonary disease (COPD), and 22 patients with primary bronchogenic carcinoma. A bronchoalveolar lavage (BAL) was performed in all subjects (both sides in 13 oncological patients, one side in the others) and samples of BALF and blood were submitted to biochemical analysis. Results: As a lung tumor marker, BALF ferritin showed 54% sensitivity and 93% specificity and serum ferritin 22% sensitivity and 93% specificity. A significant difference was observed between the two sides in the cancer patients (p = 0.033), and between BALF ferritin from the affected side and COPD patients (p = 0.025). Greater differences were obtained when BALF ferritin in the affected side of cancer patients was compared with values in both control nonsmokers (p < 0.0001) and control smokers (p < 0.001). Conclusions: These findings seem to confirm the relative diagnostic value of BALF ferritin as a lung tumor marker and the theory of ferritin compartmentalization. However, further studies are required to clarify the relations between iron and ferritin on the one hand and inflammation, tumorigenesis and host response on the other.