Small bowel Crohn's disease has been related to an increased incidence of small bowel adenocarcinoma, but the total number of reported cases is small. We present an interesting case of a young male patient with nephrolithiasis in childhood, an atypical intermittent history of diarrhoea also since his childhood, who developed obstructive ileus and underwent an urgent operation. The operation revealed a stenosis of the ileum owing to a mass, which proved to be a small bowel adenocarcinoma. One month later, the patient underwent a curative surgical resection of the tumour with additional lymphadenectomy, followed by chemotherapy for 6 months. Since then, the patient had mild diarrhoea but enteroclysis was normal. Approximately 2 years after the resection of the tumour, a new ileocolonoscopy demonstrated deep ulcerations of the terminal ileum and the adjacent area of the colon as well as anal ulcerations. The new biopsy specimens were convincing for Crohn's disease. There were no signs of residual or relapsing cancer. There is growing evidence that Crohn's disease is one of the triggering factors for the development of small bowel adenocarcinoma. Underlying Crohn's disease should be suspected in a young patient with an atypical history of diarrhoea and small bowel adenocarcinoma.