To evaluate the utility of endobronchial ultrasonography (EBUS) in selecting appropriate candidates with centrally located early-stage lung cancer for photodynamic therapy (PDT) with curative intent, we performed EBUS before PDT in 18 biopsy-proven squamous cell carcinomas (including three carcinoma in situ) that had been considered to be appropriate candidates for PDT by conventional bronchoscopy and high-resolution computed tomography (HR-CT). Nine lesions were diagnosed as intracartilaginous by EBUS and subsequently PDT was performed. Long-term complete remission has been achieved in these patients with a median follow-up term after PDT of 32 months. The remaining nine lesions were diagnosed as extracartilaginous by EBUS and were considered candidates for other therapies such as surgical resection, chemotherapy, and radiotherapy, although two were invisible by HR-CT, three were superficial, and five were < or = 1 cm in diameter on observation by bronchoscopy. The depth of tumor invasion estimated by EBUS was proven to be accurate by histopathologic findings in six specimens after surgical resection. We conclude that EBUS is a useful technique that might be considered in addition to conventional bronchoscopy and HR-CT to improve the efficacy of PDT in patients with centrally located early-stage lung cancer.