The possibility that low-calorie sweeteners (LCS) promote lower quality diets and, therefore, weight gain has been noted as a cause for concern. Data from a representative sample of 22,231 adults were obtained from five cycles of the National Health and Nutrition Examination Survey (1999-2008 NHANES). A single 24-hour recall was used to identify consumers of LCS beverages, foods and tabletop sweeteners. Diet quality was assessed using the Healthy Eating Index 2005 (HEI 2005) and its multiple subscores. Health behaviors of interest were physical activity, smoking and alcohol use. LCS consumers had higher HEI 2005 scores than did non-consumers, largely explained by better SoFAAS subscores (solid fats, added sugar and alcohol). LCS consumers had better HEI subscores for vegetables, whole grains and low-fat dairy, but worse subscores for saturated fat and sodium compared to non-consumers. Similar trends were observed for LCS beverages, tabletop LCS and LCS foods. Consumers of LCS were less likely to smoke and were more likely to engage in recreational physical activity. LCS use was associated with higher HEI 2005 scores, lower consumption of empty calories, less smoking and more physical activity.