LUNG CANCER IS THE FIRST CAUSE OF DEATH BY MALIGNANCIES IN MEXICO, THE PRINCIPAL RISK FACTOR FOR LUNG CANCER IS SMOKING BECAUSE IS PRESENT IN ABOUT 90% OF THE CASES, ADDITIONALLY, IT HAS BEEN IDENTIFIED ENZYMATIC POLYMORPHISM THAT INFLUENCE IN THE ACTIVATION AND ELIMINATION OF XENOBIOTICS FOUND IN THE SMOKE OF THE CIGAR. LUNG CANCER HAS A WIDE RANGE OF CLINICAL PRESENTATIONS THAT DEPENDS OF THE TUMOR LOCATION AND THE CELLS LINAGE, THOSE PRESENTATIONS APPEARS IN LOW AIRWAYS, THE PARANEOPLASTIC SYNDROMES, SKIN MANIFESTATIONS AND OTHERS THAT ARE MANIFESTED IN DIFFERENT STAGES OF THE SICKNESS. FOR DIAGNOSIS, IT IS ESSENTIAL TO MAKE A THOROUGH CLINIC HISTORY AND PHYSICAL EXPLORATION, WHICH STRONGLY SUGGEST THE PRESENCE OF THIS MALIGNANCY. ADDITIONALLY SPUTUM CYTOLOGY, BIOPSY, HISTOCHEMICAL STAINS AND IMMUNOHISTOCHEMISTRY ARE USED. PROGNOSTIC DEPENDS OF THE CELL LINAGE, PATIENT CLASSIFICATION AND THE TREATMENT USED.