OBJECTIVE: To calculate the proportion of cancer cases in the Netherlands in 2010 that were attributable to lifestyle factors by using the most recent data. DESIGN: Secondary analysis. METHOD: Lifestyle risk factors studied were tobacco smoking, alcohol consumption, overweight, lack of physical exercise, and six elements of diet (consumption of vegetables, fruit, processed meat and red meat, and calcium and fibre intake). The lifestyle factors were organised so that the group with the highest risk (e.g. smokers) could be compared with the groups with the lowest risk (e.g. ex-smokers, non-smokers). Cut-off points were in line with Dutch public health messages. We obtained prevalence data on risk factors from national databases. Relative risks for the relationship between lifestyle and cancer were based on the international literature. Incidence and mortality data for cancer in 2010 were obtained through the Netherlands Cancer Registry. We calculated percentages of new cancer cases and deaths for men and women and for each type of cancer individually; these were then summed. RESULTS: We estimated that of the 98,971 newly-diagnosed cases of cancer among persons aged ≥ 20 years in the Netherlands in 2010, 29,938 (30%) were attributable to the above-mentioned lifestyle factors. Smoking was the most important contributory risk factor (19% of all new cancer cases), followed by sub-optimal dietary habits (10%), overweight (4%), alcohol consumption (3%), and lack of physical activity (2%). Of cancer deaths in 2010, an estimated 38% were attributable to lifestyle factors. Projections for 2020 show that lack of exercise and consumption of alcohol and meat will contribute less to the development of cancer while overweight and a reduction in inadequate dietary fibre intake and inadequate fruit and vegetable consumption will contribute more. CONCLUSION: Almost one-third of all cases of cancer and almost 40% of deaths from cancer can be attributed to a less healthy lifestyle.