Smoking is the major cause of lung, laryngeal and bladder cancer. The exact mechanisms of carcinogenic substances in tobacco smoke are not known, but signaling pathways mediated via cyclooxygenase and its derivatives are considered the most important mechanisms. Cessation of smoking lowers the risk of disease at all ages. Besides increasing the risk of developing cancer, smoking also worsens the prognosis of a cancer patient and increases adverse effects of cancer treatments. Cessation of smoking is an essential part of appropriate cancer therapy resulting in positive effect on the prognosis and quality of life of the patient.