Smoking is recognized as a health problem worldwide and there is an established tobacco epidemic in Saudi Arabia as in many other countries, with tobacco users at increased risk of developing many diseases. This cross sectional study was conducted to assess the prevalence of oral mucosal, potentially malignant or malignant, lesions associated with tobacco use among a stratified cluster sample of adults in Jeddah, Saudi Arabia. A sample size of 599 was collected and each participant underwent clinical conventional oral examination and filled a questionnaire providing information on demographics, tobacco use and other relevant habits. The most common form of tobacco used was cigarette smoking (65.6 %) followed by Shisha or Moasel (38.1%), while chewing tobacco, betel nuts and gat accounted for 21-2%, 7.7%, and 5% respectively. A high prevalence (88.8%) of soft tissue lesions was found among the tobacco users examined, and a wide range of lesions were detected, about 50% having hairy tongue, 36% smoker's melanosis, 28.9% stomatitis nicotina, 27% frictional keratosis, 26.7% fissured tongue, 26% gingival or periodontal inflammation and finally 20% leukodema. Suspicious potentially malignant lesions affected 10.5% of the subjects, most prevalent being keratosis (6.3%), leukoplakia (2.3%), erythroplakia (0.7%), oral submucous fibrosis (0.5%) and lichenoid lesions (0.4%), these being associated with male gender, lower level of education, presence of diabetes and a chewing tobacco habit. It is concluded that smoking was associated with a wide range of oral mucosal lesions , those suspicious for malignancy being linked with chewable forms, indicating serious effects.