Int. J. Environ. Res. Public Health 2009, 6 1. Introduction 609 According to the World Health Organization (WHO), cigarette smoking is the second major cause of death in the world, with about five million deaths each year [1]. Many developed countries have joined the “global war” on smoking launched by the WHO, with extensive tobacco control policies including high cigarette taxes, smoking bans in enclosed public places, restrictions on advertising and selling, as well as public education campaigns and health warnings on cigarette packs. In France, cigarette smoking causes every year about 60,000 premature deaths [2], and the social cost of smoking has been estimated at 1.1% of the Gross Domestic Product [3]. Tobacco control has become a priority for the French government, who strengthened its anti-tobacco policy in the early 2000s. The spearhead of this policy was a sharp increase in cigarette taxes. Indeed, between 2000 and 2008, the French government raised cigarette prices by 66% (from 3.20 € to 5.30 € per pack), and a further increase is planned in 2009. As a result, between 2000 and 2005 the smoking prevalence among the French population declined slightly, from 33% to 30% [4]. Concurrently with the strengthening of tobacco control policies, previous studies conducted in several developed countries concluded that cigarette smoking was increasingly correlated to socio- economic disadvantage. In the UK, Marsh and McKay found that since the 1970s the smoking prevalence halved among professional and managerial categories, but fell only by one third among unskilled manual workers [5], and another longitudinal study concluded that the social differentiation of smoking increases across the life-course [6]. In other European countries, the smoking prevalence is higher among the least qualified individuals [7], and this relationship has amplified between 1985 and 2000 (especially in Scandinavia, Germany, Italy, Spain) [8,9]. Regarding the USA, Franks et al. [10] found that increased real cigarette-pack price over time was associated with a marked decline in smoking among higher-income people, but not among lower-income people. Other studies found that living under the poverty threshold is correlated with smoking, even after adjusting for the effects of several confounders (depression, other substance abuse) [11,12]. Moreover, in both the UK and the USA, poor smokers are claimed to be “poor quitters”: the most deprived smokers attempt to quit as frequently as others, but succeed a lot less frequently [6,13]. These converging results suggest that anti-tobacco policies, after having gained ground in all social environments, are now up against a "hard core" of smokers, less sensitive to price increases, and concentrated in the most underprivileged social strata [10,14]. This increasing association of enduring smoking with markers of social disadvantage has raised concern among public health experts [15]. The aims of the present article were two-fold. Firstly, we studied the social differentiation of cigarette smoking in France between 2000 and 2008, using quantitative data extracted from several national surveys. We hypothesised that during the 2000s the decrease in smoking prevalence was less pronounced among low socioeconomic status populations. Secondly, in order to better understand why poor smokers are less sensitive to price increases, we investigated their smoking habits and motives using both quantitative and qualitative data. Quantitative data extracted from a national representative telephone survey conducted in 2008 were used to compare poor smokers and other smokers‟ motives, and in-depth interviews carried out with poor smokers were used to specifically study their smoking motives.