Tobacco smoking is an independent risk factor in the etiology of Crohn's disease, functional dyspepsia, GERD, chronic pancreatitis and gastrointestinal carcinomas (oesophagus, stomach, colon, pancreas and liver). The current knowledge of the effects of tobacco smoking on the gastrointestinal tract is summarised. Non-smoking should be recommended to everybody as primary prevention against cardiopulmonary and gastrointestinal diseases. Despite lacking of clinical studies tobacco abstinence should be recommended as a secondary preventive therapy of Crohn's disease, functional dyspepsia, GERD and chronic pancreatitis because of epidemiological studies and pathophysiological considerations. All gastroenterologists should help patients with the above mentioned diseases to stop smoking. Evidence based methods of smoking cessation and methods suited to routine clinical care are presented. Pharmacological (nicotine replacement therapy) and psychological therapies (cognitive behavioural group therapies) should be adapted to the prior experiences of the patient, his stage of motivation to stop smoking and his co-morbidity. In refractory ulcerative colitis controlled tobacco smoking can be recommended to ex-smokers.