We describe a patient with adenocarcinoma of the lung who developed hydronephrosis secondary to compression by right common iliac lymph node metastases. The most common primary sites of cancers causing ureteral obstruction are the cervix, prostate, bladder and colo-rectum. To date, few reports of ureteral obstruction attributable to lung cancer have been published. Although rare, physicians should be aware that hydronephrosis can complicate the course of patients with non-small cell lung cancer.