Bone metastases occur in 30-40% of patients with lung cancer. Recent studies have demonstrated positive antitumor effects with zoledronic acid (ZOL). However, whether ZOL exerts antitumor activity for lung cancers remains unclear. An 87 year-old male referred to our hospital for investigation of an abnormal shadow on chest X-ray. Chest CT revealed a 74×46 mm mass at the left upper lobe (S¹⁺²), and an osteolytic change in the thoracic vertebra. PET showed accumulations at the spine, left clavicle, left multiple ribs, right scapula, and right humerus. This patient was diagnosed with pulmonary adenocarcinoma having multiple metastases of the brain and bone by sputum cytology. He received only ZOL because of his advanced age and performance status. A chest X-ray was performed after four administrations of ZOL, which revealed that the mass shadow at the left upper lung field was remarkably reduced. Chest CT revealed that the size of the mass had decreased (66×38 mm), and an improvement in QOL was noted after ZOL monotherapy. We believe this case may have demonstrated possible antitumor effects of ZOL for non small cell lung cancer.