Flat adenomas of the colon and duodenum have been described as associating with familial adenomatous polyposis (FAP), its attenuated variant, and the so-called hereditary nonpolyposis colorectal cancer. There seem to be no report on the occurrence of flat adenomas in pediatric patients with family history of FAP. We are reporting 4 children from 2 cancer-prone families in whom colonic and duodenal moderately dysplastic flat adenomas were found. Gastrointestinal endoscopy and biopsies were performed in 3 female siblings (7, 9, and 11 years old) and 1 male (9 years old) when referred for screening owing to familial history of bowel cancer (family 1) or evidence of bilateral congenital hypertrophy of the retinal pigment epithelium (CHRPE), which is known to be associated with FAP (family 2). Endoscopic visualization of the mucosa was improved by use of 0.2% indigo carmine solution spray. Biopsies were routinely processed for H&E and immunohistochemistry staining. Present patients were asymptomatic, with the exception of 2 weeks rectal bleeding in 1 of them. The colonic videoendoscopy showed in 2/3 siblings hundreds of flat or slightly raised plaques less than 1 cm in diameter as well as some classic polyps throughout the colon. The other sibling showed 40 flat-topped lesions with minimal elevation and central umbilication in the cecum. Upper endoscopy demonstrated a few flat lesions in the nonperiampullary area of the duodenum in 2/4 patients. The colonic videoendoscopy performed on the 9-year-old boy revealed multiple small sessile polyps. Microscopic study demonstrated tubular adenomas with a few neoplastic crypts, slight disarray of the overall architecture, and moderate (low-grade) dysplasia of the epithelium. These features were more obvious at the center and superficial areas of the adenomas. The 4 children had multiple flat adenomas of the colon and duodenum (2/4) matching with those described in adult patients. Flat adenomas in the context of FAP probably represent early stages of the adenoma development. Careful endoscopic-histologic correlation may result in increasing recognition of these lesions at the pediatric age.