Background: Urinary bladder dysfunction is a major complication of diabetes mellitus and its mechanism has been attributed to autonomic and/or peripheral neuropathy. Objectives: Evaluation of diabetes mellitus and neuropathy effect on the urinary bladder dynamics in children and adolescents with Type 1 diabetes mellitus. Patients and Methods: The study included 80 children and adolescents with Type 1 diabetes for at least 5 years; 60 patients were with manifestations of autonomic and/or peripheral neuropathy and 20 patients were free of either. We assessed both groups for presence of cystopathy by means of uroflowmetry and cystometry. Results: All patients with diabetic neuropathy had abnormal urodynamic test results of variable types and degrees with bladder hypercompliance as the most frequent abnormality. Other urodynamic abnormalities were found in both diabetic patients’ groups with no significant difference in frequency. Conclusions: Diabetic neuropathy might be strongly related to urodynamic abnormalities particularly the bladder hypercompliance. Some diabetic patients may have cystopathy in absence of evident neuropathy. This may be due to undetected neuropathy or diabetes induced myopathy of the detrusor muscle.