['Declining lung cancer rates in California have been attributed to the California Tobacco Control Program, but may reflect earlier declines in smoking.', 'Using state-taxed sales and three survey series, we assessed trends in smoking behavior for California and the rest of the nation from 1960 to 2008 and compared these with lung cancer mortality rates. We tested the validity of recent trends in state-taxed sales by projecting results from a model of the 1960 to 2002 data.', 'From 1960 to 2002, the state-taxed sales and survey data are consistent. Californians initially smoked more than the rest of the nation, but cigarette consumption declined earlier, dropping lower in 1971 with an ever widening gap over time. Lung cancer mortality follows a similar pattern, after a lag of 16 years. Introduction of the California Tobacco Control Program doubled the rate of decline in cigarette consumption. From 2002 to 2008, differences in enforcement and tax evasion may compromise the validity of the taxed sales data. In 2010, smoking prevalence is estimated to be 9.3% in California and 17.8% in the rest of the nation. However, in 2008, for the first time, both cigarette price and tobacco control expenditures were lower in California than the rest of the nation, suggesting that the gap in smoking behavior will start to narrow.'] Does forty years of faster decline in cigarette smoking in California explain current lower lung cancer rates?