THE letter from Chan Yue-chow (South China Morning Post, December 20), reveals a misconception about the power of advertising which many people share, and deserves to be corrected. Advertising cannot make people do anything they don't want to do, and it cannot create an interest where none exists. This is especially true of tobacco advertising, particularly because there are many other, very high profile messages conveyed by government and various organisations telling people not to smoke. There is a wealth of independent evidence which shows that advertising does not influence people to smoke. As a matter of fact, many countries which ban tobacco advertising experience increases in smoking. For example, Norway imposed a ban in 1975 and saw tobacco consumption per head rise by 1992 by three per cent. Iceland (which banned advertising in 1977) has had a rise of 21 per cent, and Finland (1978) five per cent. Singapore banned advertising in 1971 and has seen the number of young male smokers (aged between 15 and 19) increase by 100 per cent between 1987 and 1991. Although people are obviously conscious of tobacco advertising and brand names, that consciousness does not cause them to take up smoking. Awareness of an advertisement is one thing, a decision to smoke is quite another. While there has been plenty of research into the effect of tobacco advertising on children which shows that children are aware of advertising, none establish a causal connection between advertising and starting to smoke. In his article in the International Journal of Advertising (Vol XII No 3 1993) Mr Colin McDonald, a leading UK market researcher, comments that anti-smoking organisations which claim that a correlation exists between awareness of advertising and smoking 'fail to establish a causal link, relying instead on emotive language to convey the impression of cause and effect'. Independent research consistently shows that peer pressure and the influence of family are the decisive reasons why young people take up smoking. This was reflected in a recent report called Why Children Start Smoking prepared in 1991 by the UK Office of Population Censuses and Surveys - a government body. It summarised the major factors why young people start to smoke. Advertising was not listed. In the light of all this persuasive evidence the layman will legitimately respond with the question: 'Why, then, do tobacco companies advertise?' Like any other companies operating in an established market, they seek to maintain brand loyalty among existing users and try to get them to switch brands. I hope this helps Mr Chan, and many other readers unfamiliar with the complexities of advertising, to understand the situation a little better. Furthermore, I would like to emphasise that under its voluntary code of practice, the tobacco industry maintains a policy of directing its marketing activities towards existing adult smokers only and the Tobacco Institute is committed to a policy of preventing young people from starting to smoke. Currently we are planning to sustain this effort by launching another youth no-smoking programme for 1995, the details of which will be announced shortly.