Purpose: To evaluate knowledge of betel quid (BQ) vendors in relation to traditional chewing and smoking habits in Northern Thailand. Materials and Methods: Interviews of vendors selling BQ and other traditional chewing and smoking items were conducted. Questions related to side effects of BQC were included, as well as questions focusing on why traditional chewing and smoking habits were on the decline. Results: Nineteen stalls in 10 markets were visited and 18 vendors were interviewed (16 women, 2 men, average age 55.0 years, range 28-75 years). Vendors had been present for an average of 21.8 years (range 2-60 years). The number of customers buying BQ regularly was 2-3 per day. More elderly women than men bought BQ. Side effects of BQ on the oral mucosa were largely unknown to vendors. Most respondants thought BQ to be good for teeth. Reasons why young people have given up the BQ habit were black teeth. Miang (fermented tea leaves) and khi yo (traditional cigar) were rarely sold and were considered vanishing habits. Conclusions: BQ vendors had poor knowledge of the side effects of BQC. BQ vendors unanimously considered traditional habits such as chewing of BQ, miang and smoking of traditional cigars to be on the decline. Nowadays, most of these items are bought to be offered during ceremonies. Generally, traditional habits seem to be replaced by 'modern' lifestyle habits such as cigarette smoking and alcohol consumption. With these changes, general and oral disease patterns will eventually occur. Schlagwörter: areca nut, betel quid chewing, tobacco, oral cancer