Carcinoma of the colon and rectum is very rare in childhood and adolescence. We describe a 16.5-year-old girl with rectal bleeding and constipation. She had been treated symptomatically for 6 months without being properly examined. Only with onset of weight loss was rectal examination performed. After workup a diagnosis of locally advanced carcinoma of the rectosigmoid with multiple lung metastases was reached. From review of the literature and our own case, it seems that the unfavorable prognosis in young patients is mainly due to lack of awareness of such a possibility, resulting in delayed diagnosis and treatment. An additional factor is the invasive nature of most colon cancers in this age group.