Gambling is a worldwide phenomenon. For most persons this causes only small or no problems, but for some, pathological gambling can be the result of entering the gambling environment. The objectives were to estimate the past year and lifetime prevalence of problem gambling in the adult Danish population (16 years or older) in 2010 and trends since 2005 and, furthermore, to investigate whether problem gamblers differed from non-problem gamblers with regard to sociodemographic and socioeconomic factors. Data were derived from two national representative Danish health surveys. The survey in 2005 was based on region-stratified random sample of 10,916 Danish citizens (response rate: 52.1 %) and the survey in 2010 was based on a random sample of 23,405 Danish citizens (response rate: 62.7 %). Problem gambling was defined using the lie/bet questionnaire. The past year prevalence of problem gamblers in Denmark remained stable from 2005 to 2010 (0.9 and 0.8 %, respectively). The highest past year prevalence of problem gamblers was found among young men in both 2005 and 2010. Furthermore, problem gamblers were more prevalent among men, disability pensioners, less educated and those not married or cohabiting. The present study indicates that a high level of education and being employed have a protective effect against problem gambling. More research is needed in order to understand what attracts and maintains the interest of men in gambling environments as well as why women are not occupied by gambling in the same degree as men.