This study explored the association between dietary habits and overweight and obesity in adolescents from Xi'an City, China. A cross-sectional sample of 1804 adolescents was recruited in 2004 from 30 junior high schools in six districts of Xi'an City, northwest China. Weight and height was measured and eating habits assessed using a self-administered questionnaire. Logistic regression was used to identify dietary patterns associated with overweight and obesity and adjusted for socio-demographic factors. Consumption of foods and beverages outside three main meals, and potato chips was more popular in boys than in girls, while girls consumed more fried food and soft drinks than boys. In boys, an increased consumption of soft drinks was associated with increased risk of overweight and obesity (1100 mL/day, OR: 1.9, 95% CI: 1.1-3.8), while consuming preserved fruit was associated with decreased risk (OR: 0.6, 95% CI: 0.5-0.9). In girls, having breakfast outside the home (OR: 1.7, 95% CI: 1.1-2.3) and an increased consumption of energy-dense foods (OR: 1.7, 95% CI: 1.04-2.9), was associated with increased risk of overweight and obesity, while frequently having foods and beverages outside the three main meals (OR: 0.6, 95% CI: 0.4-0.9) was associated with decreased risk. The consumption of breakfast outside the home, soft drinks and energy-dense fast foods were positively associated with overweight and obesity in adolescents. Future health education programs to prevent excess weight gain should target such unhealthy eating habits.