OBJECTIVES: To assess the use of Internet-based portals among families of children with chronic diseases and to describe characteristics of portal registrants and users. DESIGN: Retrospective observational study. SETTING: Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, using data from September 1, 2003, through February 29, 2008. Patients/ PARTICIPANTS: Parents of children with diabetes mellitus, juvenile idiopathic arthritis, or cystic fibrosis. INTERVENTIONS: Parents of children with a chronic disease were given the opportunity to access health-related information for their children via an Internet-based portal. OUTCOME MEASURES: Percentage of families who obtained a portal account (registered), used the portal for the first time within 3 months and again 3 to 6 months after registration, number of times logged in, and session length. RESULTS: Of 1900 families, 27.9% obtained a portal account. Of those, 47.8% used the portal within 3 months of registration and 15.9% continued to use the portal 3 to 6 months after registration. Families of African American patients and of patients insured by Medicaid were less likely to obtain a portal account. More outpatient visits and having private health insurance coverage were associated with increased portal registration and use. CONCLUSIONS: Understanding the feasibility of portal use by parents is an important first step to using portals for improving self-management, patient-provider interactions, and outcomes for children with chronic diseases. Subsequent studies should address parent perceptions of the value portals add to the management of the chronic disease of their child and ways to increase that value. Barriers to using portals among racial minorities and publicly insured families should also be studied to address disparities.