The second phase of the SIDRIA study provides important information regarding the family characteristics of Italian children (6-7 years old) and adolescents (13-14 years old), and the frequency of risk factors for asthma and allergies, allowing comparisons between study areas according to differences in latitude (North, Centre, South) and urbanization level (metropolitan areas, with at least 500,000 inhabitants, and other areas). Parental education level was higher in metropolitan and central areas. The frequency of children and adolescents born abroad, and the percentage of mothers and fathers employed were higher outside metropolitan areas and there was an increase from the South to the North of Italy. This trend was paralleled by an increase in maternal age at child's birth and in the frequency of low birth weight and day care attendance. The frequency of breastfeeding was greater in children than in adolescents; the opposite was registered for passive smoking, with a frequency of exposure higher in adolescents than in children, especially in the Northern and Central areas, even if the proportion of subjects having at least one parent who smokes was still high in both age groups. The prevalence of overweight children was striking, especially in the South where physical activity was less frequent and children had the unhealthy habit of consuming a lot of snacks and carbonated beverages. Frequency of exposure to traffic in the area of residence was particularly high, especially in the metropolitan areas.