Adenocarcinomas of colon are very uncommon in children. Two 13 years old boys with colon adenocarcinoma who have been tried to be managed in our department, have been presented. The first case who has come with acute intestinal obstruction, has diagnosed as sigmoid volvulus. Adenocarcinoma of the sigmoid colon (Dukes C 2) has been detected at the operation. In the other case hydronephrosis and loss of the renal function has been thought to be due to nephrolithiasis. On operation, it was found that the tumor invading the right kidney was the metastasis of the mucinous adenocarcinoma of the sigmoid colon (Dukes C2). Malignancy was not suspected in both cases because of the acute intermittent and nonspesific characteristics of the symptoms. Since the tumors in both cases were metastatic, the therapy has been unsuccessful and the patients have died within 6 and 1.5 months respectively. Carcinoma of the colon is generally diagnosed late in children. Because of its rarity in the pediatric age group, it is not considered in the diagnosis. The symptoms are usually nonspesific and findings may be underestimated. Mucinous adenocarcinoma which grows and extends rapidly is the most common histologic type seen in children. Therefore, the prognosis of the adenocarcinomas of the colon in the children is very poor and the early diognosis is very important.