Intraocular metastases, especially to the retina, are uncommon in cancer patients and generally occur in an advanced phase of the disease. In patients with lung cancer, uveal metastases, in particular to the choroid, are the most frequent, and are associated mainly with small cell carcinoma or undifferentiated carcinoma. We report a case of unilateral retinal detachment as first sign of a moderately differentiated lung adenocarcinoma in a 55-year-old non-smoker that was admitted to the hospital for the first time complaining of a sudden visual loss in the superior fields of the left eye. A CT revealed a slight retinal enlargement of the left eye and a solid mass of about 3 centimeters behind the right pulmonary hilus. Bronchoscopic biopsies were performed with diagnosis of adenocarcinoma of the lung. The patient died after 2 months for rapid progression of the disease despite of combined chemotherapy treatment.