Previous research has demonstrated a clustering of positive health behaviors; individuals with good health practices probably act in a similar way towards other health behaviors. The hypothesis of this study was that lifestyle patterns (smoking, alcohol consumption, and physical activity) influence diet quality and nutrition knowledge, attitudes, beliefs and behaviors. Subjects were 1425 adults who completed USDA's 1994 Continuing Survey of Food Intakes by Individuals and Diet and Health Knowledge Survey. Cluster analysis divided subjects into three groups (Healthy, Moderate and Hedonistic) based on their smoking, alcohol consumption, and physical activity. These groups were compared on their diet quality, knowledge of nutrition, attitudes towards food/nutrition, beliefs about diet and health, and food preparation behaviors using analysis of variance. We found that subjects in the Healthy group (who smoked and drank less, and exercised more) had higher diet quality scores, more positive attitudes, and healthier food preparation behaviors than subjects in the Hedonistic and Moderate groups; and higher knowledge scores and more positive beliefs than the Moderate group. These findings suggest that adults with healthy lifestyle patterns also make good diet choices, and these choices may be influenced by greater knowledge and more positive attitudes and beliefs about nutrition.