INTRODUCTION: Lower urinary tract dysfunction (LUTD) involves faults in the filling and emptying phases of bladder function in toilet-trained children with no previous infection or any other obvious pathology. Lower urinary tract dysfunction is associated with conditions such as vesicoureteral reflux, recurrent urinary infection, behavioral alterations and decreased quality of life. The literature suggests an association between LUTD and obesity; however, the association between each individual symptom and obesity has yet to be evaluated. OBJECTIVE: To evaluate the association between excess weight and LUTD in children and adolescents in a community-based sample. STUDY DESIGN: This cross-sectional study included 423 children and adolescents aged 5-17 years, and randomly selected in public places and schools between May and July 2015. The participants and their mothers completed the Dysfunctional Voiding Scoring System (DVSS) questionnaire, except for the questions on constipation and with the addition of a question on enuresis. They also completed the Rome III questionnaire, in which two positive responses defined the presence of constipation. Participants were classified as being of normal weight, overweight or obese, which was based on the BMI-for-age indicator. RESULTS: Mean age was 9.7 years (SD 2.9), with girls comprising 50.6% of the sample and adolescents 52.5%. The prevalence of LUTD was 7.1%, with 13.5% of participants being overweight and 12.1% obese (Figure). Constipation was present in 5.9% of participants and enuresis in 10.8%. In the multivariate analysis, three factors were independently and significantly associated with a positive DVSS: age <10 years (ß = 0.76; 95% CI: 0.34-1.18), constipation (ß = 1.79; 95% CI: 0.88-2.70) and obesity (ß = 0.89; 95% CI: 0.25-1.52). DISCUSSION: Only bladder filling symptoms were associated with obesity. This may be explained by the fact that both obese individuals and those with emptying symptoms were shown to have activation alterations in the same brain regions. One limitation of this study was the use of questionnaires alone to diagnose LUTD and constipation. CONCLUSION: Only the bladder-emptying symptoms of LUTD appear to be associated with obesity. This hypothesis may serve as a basis for future studies.