A prospective study was performed to evaluate the prevalence of suspected dysfunctional voiding (DV) and associated risk factors in children with asthma. The DV is defined as any voiding symptoms and/or urinary incontinence. Children (4–10-year-old) with asthma (n=178) and healthy subjects (n=197) were enrolled. DV and Incontinence Scoring System were administrated. Demographic features and asthma related characteristics were recorded. Suspected DV was noted in 19 (27.9%) of patients with asthma and 5 (6.6%) of healthy subjects in children younger than 6 years of age (p=0.001). In this patient group, asthma increased the risk of suspected DV (OR=5.7 (95% CI 1.988 to 16.344)). Children with asthma older than 6 years of age had similar prevalence of suspected DV but they had higher frequency of voiding and urgency. Asthma is associated with higher DV symptom scores in younger children who have already completed toilet training and with some of DV symptoms such as frequency and urgency in older children.