Introduction: The aims of the study are to validate and further psychometrically test the five-dimensional structure of the Reasons for Gambling Questionnaire (RGQ), and to test the differences between different types of gamblers (i.e., offline gamblerswho gambled in-person only vs. mixed-mode gamblerswho gambled both online and offline) on the five dimensions of the RGQ. Methods: Data from the 2010 British Gambling Prevalence Survey (BGPS) were used. The analyzed data comprised 5677 individuals (52.7% female; mean age = 47.64 years; SD = 17.82). Confirmatory factor analysis and independent-sample t-tests were applied. Results: The five-dimensional structure of the RGQ was confirmed in the general sample and among gender and age subgroups. Furthermore, mixed-mode gamblers (MMGs) who gambled both online and offline had higher scores for enhancement, recreation and money motives than offline gamblers that gambled in-person only (IPGs). In addition among males, there was a significant difference in the scores for enhancement and recreation motives across MMGs and IPGs. Among past-year gamblers aged 16–34 years, MMGs had higher scores for enhancement, recreational and monetary motives than IPGs while among past-year gamblers aged 35–55 years, MMGs had higher scores for enhancement and recreational motives than IPGs. Conclusions: The results are consistent with a previous test of the RGQ and the findings indicate that the RGQ is a valid instrument to assess gambling motives among the general population.