The prevalence of asthma and obesity, two often associated conditions, is influenced not only by age and gender but also by lifestyle factors. This study aimed to determine whether, in a Mediterranean northern Italian region, Liguria, an increased prevalence of obesity could be detected in asthmatic children and adolescents and to evaluate the possible relationship between body mass index (BMI) and the characteristics and/or severity of asthma. BMI was determined in 554 asthmatic subjects (2.2-16.1 years) and 625 age-matched controls; BMI was expressed as a continuous variable in standard deviation score (SDS) units, determined as difference between the individual observed value and the reference mean for age and sex, divided by the corresponding standard deviation (BMI-SDS). Overweight/obesity was set at BMI-SDS of 2 or more. BMI-SDS was significantly higher in controls than in asthmatics (p = 0.04); however, the proportion of overweight/obesity subjects (BMI-SDS > or = 2) was similar in controls and in asthmatic patients (p = 0.08). Evaluation of the asthmatic group revealed that BMI-SDS was independent of gender (p = 0.57), atopic sensitization (p = 0.69), and comorbidity with other allergic symptoms (p = 0.60). By contrast, BMI-SDS was lower in preschool-age children than in school-age children and adolescents (p < 0.0001), in subjects with a high rate of acute respiratory tract infections (p = 0.04), and in those not treated with inhaled corticosteroids (IGCs) (p = 0.02). Although an increase in the prevalence of overweight/obesity was not detected in asthmatic children and adolescents, the results reported here suggest a preventive surveillance of calorie intake and a promotion of physical activity in children requiring long-term treatment with inhaled glucocorticosteroids.