Smoking is a serious public health problem. In Morocco, the number of smokers varies from 24% to 52% depending on different social categories (school children, university students, public health workers, industrial workers, civil servants). The aim of our descriptive study was to analyze knowledge about smoking and smoking habits in patients hospitalized or followed by two units in the Ibn Rochd Hospital, cardiology and respiratory diseases. A questionnaire was given to a consecutive series of 200 patients between January and March 1997 (100 patients in each unit). Twenty percent of the patients were smokers and 23% were former smokers. The most well known health risks of smoking in the two groups of patients were respiratory and cardiovascular risks (88% and 71% respectively). Smokers and former smokers were more aware of these health risks. 86% of the smokers and former smokers had attempted to stop smoking at least once, mainly for a "health" reasons. 60% of smokers and former smokers decided to never smoke or never take a cigarette again. 66% of the patients said they had not been advised at the hospital about the risk of smoking. Our study provides a basis for further studies. It points out the importance of the smoking phenomena and the minimal role played by health personnel in advising patients. Health care workers should participate in antismoking activities during their consultation activities at the hospital in order to help patients stop smoking and also help implement rigorous antismoking laws in Morocco.