In spite of the superiority of single agent over best supportive care in second-line NSCLC, the prognosis of these patients remains poor with a median survival of 6-7 months, justifying the evaluation of new regimens in this setting. An open question in the second-line treatment of NSCLC remains the possible superiority of combination chemotherapy over single agent, as it has been clearly demonstrated in first-line. Particularly, the addition of platinum to either docetaxel or pemetrexed should be further investigated especially in patients with prior response/stable disease to platinum-based first-line chemotherapy. Pemetrexed has shown anti-tumor activity in combination with other chemotherapy agents, including gemcitabine, vinorelbine, taxanes, cisplatin and carboplatin. In this multicenter, open label, randomized phase II trial, pemetrexed 500 mg/m2 and carboplatin AUC 5 will be administered on day 1 every 3 weeks until progression of disease or for a maximum of 4 courses in the experimental arm. The control arm will be pemetrexed as single agent at 500 mg/m2 on day 1 every 3 weeks until progression of disease or for a maximum of 4 courses.