Drug interaction is a process during which a drug's fate in the body or its pharmacological properties are altered by an influencing factor. The extent of the drug interaction's effect can vary. The interaction could result from the modulation by another drug, food, alcohol, caffeine, narcotics, a drug influencing absorption or smoking. Moreover, transporter interactions with smoking could also have a major impact on many drug's efficacy. Clinically relevant drug interactions with smoking were classified in terms of their effect: pharmacokinetic, pharmacodynamic and transporter interactions. Policyclic aromatic carbohydrates, found in cigarette smoke, have enzyme inducing properties. The interaction affects mainly the hepatic isoenzyme CYP1A2. Interactions caused by smoking have an effect on all drugs being substrates of and therefore metabolised by CYP1A2. Pharmacokinetic alteration can also occur during the absorption, distribution and elimination process. The pharmacodynamic interactions are mainly caused by the effects of nicotine, a cigarette smoke component. Through interactions, smoking could also modify the activity of transporter proteins, altering this way the ADME properties of many drugs. Since smoking is one of the deadliest artefact in the history of human civilisation, identifying drug interactions with smoking is the physician's and pharmacist's major responsibility and task. Moreover, it is necessary to identify the patient's smoking habits during a medical treatment. This review aims to investigate the main types of drug interactions (PK/PD), identify factors influencing the activity of CYP enzymes and transporters, and also summarize the mechanisms of the most important drug interactions with smoking and their clinically relevant consequences (Table II-VI.). Drugs, with effects somehow altered by smoking-interactions, have been studied.