OBJECTIVES: To investigate whether a modest number of food frequency questions are sufficient to describe sociodemographic differences in dietary habits, and to identify sociodemographic characteristics of subjects adhering to food-based dietary guidelines operationalised in a "healthy-diet index". DESIGN: Cross-sectional population survey. SUBJECTS: A total of 480 men, 515 women, aged 15-90 y. Random sample of private telephone numbers drawn from regional telephone records, geographically stratified. Participation rate 62%. METHODS: Computer-assisted telephone interviews, including six food frequency questions, a question on type of fat spreads used on bread, questions on seven sociodemographic variables. RESULTS: The summary of the healthy-diet index showed that the subjects who adhered to food-based dietary guidelines (top quintile) compared to those who did not (bottom quintile) were most often women (odds ratio (OR)=6.07; confidence interval (CI): 3.91-9.43, women vs men), of older age (OR=9.72; CI: 3.02-31.31, old age vs young), highly educated (OR=3.69; CI: 1.53-8.92, high education vs low) and living in multiperson households including children (OR=4.66; CI: 2.47-8.80, multiperson household vs single household). The results also showed that gender difference in dietary habits is associated with other sociodemographic variables. CONCLUSIONS: The selected food frequency questions proved sufficient to describe sociodemographic differences in dietary habits, and this method may be a valuable supplement to traditional quantitative dietary surveys in monitoring sociodemographic changes in eating patterns. The results also underline the influence of sociodemographic status on dietary habits. SPONSORSHIP: The Danish Nutrition Council funded the study.