Pain is a highly distressing symptom for patients with advanced cancer. WHO analgesic ladder is widely accepted as a guideline for its treatment. Our aim was to describe pain prevalence among patients diagnosed with advanced non-small-cell lung cancer (NSCLC), impact of pain on quality of life (QoL) and adequacy of pain management. Data of 1021 Italian patients enrolled in three randomised trials of chemotherapy for NSCLC were pooled. QoL was assessed by EORTC QLQ-C30 and LC-13. Analgesic consumption during the 3 weeks following QoL assessment was recorded. Adequacy of pain management was evaluated by the Pain Management Index (PMI). Some pain was reported by 74% of patients (42% mild, 24% moderate and 7% severe); 50% stated pain was affecting daily activities (30% a little, 16% quite a bit, 3% very much). Bone metastases strongly affected presence of pain. Mean global QoL linearly decreased from 64.9 to 36.4 from patients without pain to those with severe pain (P<0.001). According to PMI, 616 out of 752 patients reporting pain (82%) received inadequate analgesic treatment. Bone metastases were associated with improved adequacy and worst pain with reduced adequacy at multivariate analysis. In conclusion, pain is common in patients with advanced NSCLC, significantly affects QoL, and is frequently undertreated. We recommend that: (i). pain self-assessment should be part of oncological clinical practice; (ii). pain control should be a primary goal in clinical practice and in clinical trials; (iii). physicians should receive more training in pain management; (iv). analgesic treatment deserves greater attention in protocols of anticancer treatment.